added Arena appliances for fights on a separate server

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Arena.java

@@ -0,0 +1,380 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import com.google.gson.Gson;
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode;
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import eu.mhsl.craftattack.spawn.core.Main;
+import eu.mhsl.craftattack.spawn.core.api.server.HttpServer;
+import eu.mhsl.craftattack.spawn.core.appliance.Appliance;
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceCommand;
+import eu.mhsl.craftattack.spawn.core.util.entity.DisplayVillager;
+import eu.mhsl.craftattack.spawn.core.util.listener.DismissInventoryOpenFromHolder;
+import eu.mhsl.craftattack.spawn.core.util.listener.PlayerInteractAtEntityEventListener;
+import eu.mhsl.craftattack.spawn.core.util.server.PluginMessage;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import org.bukkit.Bukkit;
+import org.bukkit.GameMode;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.Sound;
+import org.bukkit.World;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.entity.Player;
+import org.bukkit.entity.Villager;
+import org.bukkit.event.Listener;
+import org.bukkit.potion.PotionEffect;
+import org.bukkit.scheduler.BukkitTask;
+import org.bukkit.util.Vector;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.UUID;
+import java.util.stream.Stream;
+
+/**
+ * The arena server: tribune, start pads, arenas, fights and resets.
+ * The main server sends a copy of the player's inventory to {@code /api/arena/inventory} before connecting the player.
+ */
+public class Arena extends Appliance {
+    public enum PlayerState {
+        TRIBUNE,
+        PAD,
+        FIGHT,
+        BUILD
+    }
+
+    private record InventoryRequest(UUID player, String items) {
+    }
+
+    private final Map<UUID, PlayerState> states = new HashMap<>();
+    private ArenaWorlds worlds;
+    private ArenaSettings settings;
+    private Teams teams;
+    private ArenaResetter resetter;
+    private final List<ArenaSlot> slots = new ArrayList<>();
+    private @Nullable Lobby lobby;
+    private @Nullable DisplayVillager.ConfigBound villager;
+    private @Nullable BukkitTask tickTask;
+
+    public Arena() {
+        super("arena");
+    }
+
+    @Override
+    public void onEnable() {
+        this.worlds = new ArenaWorlds();
+        this.villager = new DisplayVillager.ConfigBound(this.localConfig(), villager -> {
+            villager.customName(Component.text("Zurück zu CraftAttack", NamedTextColor.GOLD));
+            villager.setProfession(Villager.Profession.CARTOGRAPHER);
+            villager.setVillagerType(Villager.Type.PLAINS);
+        });
+        this.villager.getVillager().addScoreboardTag(Displays.MANAGED_TAG);
+        this.start();
+    }
+
+    @Override
+    public void onDisable() {
+        this.stop();
+    }
+
+    /**
+     * Reads the settings and builds pads, arenas and displays. Separate from onEnable so setup changes
+     * can be applied without restarting the appliance.
+     */
+    private void start() {
+        this.settings = ArenaSettings.read(this.localConfig(), this.worlds.play());
+        this.teams = new Teams();
+        this.resetter = new ArenaResetter(this.worlds, this.settings.resetBlocksPerTick());
+
+        this.settings.arenas().stream()
+            .filter(ArenaSettings.Slot::isComplete)
+            .forEach(slot -> this.slots.add(new ArenaSlot(slot, this.worlds.play())));
+        this.settings.arenas().stream()
+            .filter(slot -> !slot.isComplete())
+            .forEach(slot -> Main.logger().warning("Arena '" + slot.name() + "' is incomplete (region, spawn1, spawn2) and stays disabled"));
+
+        if(this.settings.padsComplete()) this.lobby = new Lobby(this, this.settings.pads());
+        else Main.logger().warning("Arena: pads are not set up, fights cannot be started");
+
+        this.syncRegions().forEach(region -> this.worlds.keepLoaded(region, Main.instance()));
+        this.placeStarterPlatform();
+        this.syncAll();
+
+        Bukkit.getOnlinePlayers().stream()
+            .filter(player -> this.state(player) != PlayerState.BUILD)
+            .forEach(this::toTribune);
+        this.tickTask = Bukkit.getScheduler().runTaskTimer(Main.instance(), this::tick, 1, 1);
+    }
+
+    private void stop() {
+        if(this.tickTask != null) this.tickTask.cancel();
+        this.slots.forEach(slot -> {
+            if(slot.fight != null) slot.fight.abort();
+            slot.remove();
+        });
+        this.slots.clear();
+        if(this.lobby != null) this.lobby.shutdown();
+        this.lobby = null;
+        this.resetter.cancel();
+        this.teams.clear();
+        this.worlds.releaseChunks(Main.instance());
+    }
+
+    public void reload() {
+        if(this.slots.stream().anyMatch(slot -> slot.state == ArenaSlot.State.FIGHT))
+            throw new ApplianceCommand.Error("Es läuft gerade ein Kampf");
+        if(this.lobby != null && !this.lobby.isIdle())
+            throw new ApplianceCommand.Error("Gerade steht jemand auf einem Startfeld");
+        this.stop();
+        this.start();
+    }
+
+    /**
+     * Copies the whole tribune area and all arenas from the template.
+     */
+    public void syncAll() {
+        this.slots.forEach(slot -> slot.state = ArenaSlot.State.RESET);
+        List<Region> regions = this.syncRegions();
+        for(int i = 0; i < regions.size(); i++) {
+            boolean last = i == regions.size() - 1;
+            this.resetter.reset(regions.get(i), () -> {
+                if(!last) return;
+                this.slots.forEach(slot -> slot.state = ArenaSlot.State.FREE);
+                Main.logger().info("Arena: all regions synced from the template");
+            });
+        }
+        if(regions.isEmpty()) this.slots.forEach(slot -> slot.state = ArenaSlot.State.FREE);
+    }
+
+    public boolean isBusy() {
+        return this.slots.stream().anyMatch(slot -> slot.state != ArenaSlot.State.FREE)
+            || (this.lobby != null && !this.lobby.isIdle());
+    }
+
+    private List<Region> syncRegions() {
+        return Stream.concat(
+            Stream.ofNullable(this.settings.syncRegion()),
+            this.slots.stream().map(slot -> slot.settings.region())
+        ).toList();
+    }
+
+    private void tick() {
+        this.resetter.tick();
+        if(this.lobby != null) this.lobby.tick();
+        if(Bukkit.getCurrentTick() % 10 != 0) return;
+        this.slots.forEach(ArenaSlot::updateDisplay);
+
+        // nobody takes damage outside of fights, so falling into the void would never end
+        World play = this.worlds.play();
+        play.getPlayers().stream()
+            .filter(player -> player.getY() < play.getMinHeight() - 16 && this.state(player) != PlayerState.FIGHT)
+            .forEach(this::toTribune);
+    }
+
+    /**
+     * A fresh, empty world gets a small platform at the tribune spawn, so the first visitors do not fall into the void.
+     */
+    private void placeStarterPlatform() {
+        Location spawn = this.settings.tribuneSpawn();
+        if(spawn == null) return;
+        for(World world : new World[]{this.worlds.play(), this.worlds.template()}) {
+            Location below = spawn.clone();
+            below.setWorld(world);
+            below.subtract(0, 1, 0);
+            if(!below.getBlock().getType().isAir()) return;
+        }
+        for(World world : new World[]{this.worlds.play(), this.worlds.template()}) {
+            for(int dx = -3; dx <= 3; dx++) {
+                for(int dz = -3; dz <= 3; dz++) {
+                    world.getBlockAt(spawn.getBlockX() + dx, spawn.getBlockY() - 1, spawn.getBlockZ() + dz).setType(Material.SMOOTH_STONE, false);
+                }
+            }
+        }
+        Main.logger().info("Arena: placed a starter platform at the tribune spawn");
+    }
+
+    boolean hasFreeSlot() {
+        return this.slots.stream().anyMatch(slot -> slot.state == ArenaSlot.State.FREE);
+    }
+
+    void startFight(Player red, Player blue, UUID challenger, FightMode mode) {
+        ArenaSlot slot = this.slots.stream().filter(s -> s.state == ArenaSlot.State.FREE).findFirst().orElse(null);
+        if(slot == null) {
+            this.toTribune(red);
+            this.toTribune(blue);
+            return;
+        }
+        new Fight(this, slot, red, blue, challenger, mode).start();
+    }
+
+    void resetSlot(ArenaSlot slot) {
+        if(!this.slots.contains(slot)) return;
+        slot.state = ArenaSlot.State.RESET;
+        this.resetter.reset(slot.settings.region(), () -> {
+            if(!this.slots.contains(slot)) return;
+            slot.state = ArenaSlot.State.FREE;
+            Location display = slot.settings.displayLocation(this.worlds.play());
+            Style.play(display, Sound.BLOCK_BEACON_ACTIVATE, 1.5f, 1.2f);
+        });
+    }
+
+    /**
+     * Brings the player back to the tribune with the own inventory, locked.
+     */
+    public void toTribune(Player player) {
+        if(this.lobby != null) this.lobby.leave(player);
+        this.setState(player, PlayerState.TRIBUNE);
+        this.teams.leave(player);
+        player.closeInventory();
+        Location spawn = this.settings.tribuneSpawn();
+        player.teleport(spawn != null ? spawn : this.worlds.play().getSpawnLocation());
+        restore(player, GameMode.ADVENTURE);
+        InventoryStore.apply(player, player.getUniqueId());
+    }
+
+    /**
+     * Full health and food, no effects, no fire.
+     */
+    static void restore(Player player, GameMode gameMode) {
+        player.setGameMode(gameMode);
+        player.getActivePotionEffects().stream().map(PotionEffect::getType).forEach(player::removePotionEffect);
+        player.setHealth(Objects.requireNonNull(player.getAttribute(Attribute.MAX_HEALTH)).getValue());
+        player.setAbsorptionAmount(0);
+        player.setFoodLevel(20);
+        player.setSaturation(5);
+        player.setExhaustion(0);
+        player.setFireTicks(0);
+        player.setFreezeTicks(0);
+        player.setFallDistance(0);
+        player.setArrowsInBody(0, false);
+        player.setVelocity(new Vector());
+    }
+
+    public void toggleBuild(Player player) {
+        PlayerState state = this.state(player);
+        if(state == PlayerState.BUILD) {
+            Location target = player.getLocation().clone();
+            target.setWorld(this.worlds.play());
+            this.toTribune(player);
+            if(!this.isInsideArena(target)) player.teleport(target);
+            player.sendMessage(Style.message("Bau-Modus beendet. Änderungen an der Vorlage übernimmst du mit /arenasetup sync."));
+            return;
+        }
+        if(state != PlayerState.TRIBUNE) throw new ApplianceCommand.Error("Nur von der Tribüne aus möglich");
+
+        this.setState(player, PlayerState.BUILD);
+        this.teams.leave(player);
+        Location target = player.getLocation().clone();
+        target.setWorld(this.worlds.template());
+        player.getInventory().clear();
+        player.teleport(target);
+        player.setGameMode(GameMode.CREATIVE);
+        player.sendMessage(Style.message("Du bist in der Vorlage. Mit /build kommst du zurück."));
+    }
+
+    void moveVillager(Location location) {
+        Objects.requireNonNull(this.villager).updateLocation(location);
+    }
+
+    List<String> arenaNames() {
+        return this.settings.arenas().stream().map(ArenaSettings.Slot::name).toList();
+    }
+
+    public void sendToCraftAttack(Player player) {
+        PluginMessage.connect(player, this.settings.returnServer());
+    }
+
+    public void handleQuit(Player player) {
+        Fight fight = this.fightOf(player);
+        if(fight != null && this.state(player) == PlayerState.FIGHT) fight.forfeit(player.getUniqueId());
+        if(this.lobby != null) this.lobby.leave(player);
+        this.teams.leave(player);
+        this.states.remove(player.getUniqueId());
+    }
+
+    public PlayerState state(Player player) {
+        return this.states.getOrDefault(player.getUniqueId(), PlayerState.TRIBUNE);
+    }
+
+    void setState(Player player, PlayerState state) {
+        this.states.put(player.getUniqueId(), state);
+    }
+
+    /**
+     * The fight the player is part of, also during the short celebration after it ended.
+     */
+    public @Nullable Fight fightOf(Player player) {
+        return this.slots.stream()
+            .map(slot -> slot.fight)
+            .filter(fight -> fight != null && fight.involves(player.getUniqueId()))
+            .findFirst()
+            .orElse(null);
+    }
+
+    /**
+     * Whether blocks may change at this position of the play world: only inside arenas.
+     */
+    public boolean isInsideArena(Location location) {
+        return this.slots.stream().anyMatch(slot -> slot.settings.region().contains(location.getX(), location.getY(), location.getZ()));
+    }
+
+    public @Nullable Region arenaRegionOf(Player player) {
+        Fight fight = this.fightOf(player);
+        return fight == null ? null : fight.slot().settings.region();
+    }
+
+    public @Nullable Lobby lobby() {
+        return this.lobby;
+    }
+
+    public ArenaWorlds worlds() {
+        return this.worlds;
+    }
+
+    ArenaSettings settings() {
+        return this.settings;
+    }
+
+    Teams teams() {
+        return this.teams;
+    }
+
+    @Override
+    public void httpApi(HttpServer.ApiBuilder apiBuilder) {
+        Gson gson = new Gson();
+        apiBuilder.rawPost("inventory", (request, response) -> {
+            InventoryRequest body = gson.fromJson(request.body(), InventoryRequest.class);
+            if(body == null || body.player() == null || body.items() == null) throw new IllegalArgumentException("player and items are required");
+            InventoryStore.put(body.player(), Base64.getDecoder().decode(body.items()));
+            return HttpServer.nothing;
+        });
+    }
+
+    @Override
+    @NotNull
+    protected List<ApplianceCommand<?>> commands() {
+        return List.of(new BuildCommand(), new ArenaSetupCommand(), new CraftAttackCommand());
+    }
+
+    @Override
+    @NotNull
+    protected List<Listener> listeners() {
+        UUID villager = Objects.requireNonNull(this.villager).getUniqueId();
+        return List.of(
+            new PlayerConnectionListener(),
+            new LockListener(),
+            new FightListener(),
+            new WorldProtectionListener(),
+            new ModeMenuListener(),
+            new PlayerInteractAtEntityEventListener(villager, event -> this.sendToCraftAttack(event.getPlayer())),
+            new DismissInventoryOpenFromHolder(villager)
+        );
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ArenaResetter.java

@@ -0,0 +1,127 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.ResetCursor;
+import eu.mhsl.craftattack.spawn.core.Main;
+import org.bukkit.Chunk;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockState;
+import org.bukkit.block.Container;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Player;
+import org.bukkit.util.BoundingBox;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * Copies regions from the template world over the play world. Only blocks that differ are written,
+ * without physics. Block entities (chests, signs, banners) are always copied, so changed contents are reset too.
+ * The work is spread over ticks with a fixed block budget.
+ */
+final class ArenaResetter {
+    private record Job(Region region, ResetCursor cursor, Runnable onDone) {
+    }
+
+    private final World play;
+    private final World template;
+    private final int blocksPerTick;
+    private final Queue<Job> jobs = new ArrayDeque<>();
+    private Job current;
+
+    ArenaResetter(ArenaWorlds worlds, int blocksPerTick) {
+        this.play = worlds.play();
+        this.template = worlds.template();
+        this.blocksPerTick = blocksPerTick;
+    }
+
+    void reset(Region region, Runnable onDone) {
+        this.jobs.add(new Job(region, new ResetCursor(region), onDone));
+    }
+
+    boolean isBusy() {
+        return this.current != null || !this.jobs.isEmpty();
+    }
+
+    void cancel() {
+        this.jobs.clear();
+        this.current = null;
+    }
+
+    /**
+     * Called every server tick.
+     */
+    void tick() {
+        int budget = this.blocksPerTick;
+        while(budget > 0) {
+            if(this.current == null) {
+                this.current = this.jobs.poll();
+                if(this.current == null) return;
+                this.prepare(this.current.region);
+            }
+
+            budget -= this.current.cursor.advance(budget, this::copyBlock);
+            if(!this.current.cursor.isDone()) return;
+
+            this.finish(this.current.region);
+            Job done = this.current;
+            this.current = null;
+            try {
+                done.onDone.run();
+            } catch(Exception e) {
+                Main.logger().warning("Arena: error after reset: " + e.getMessage());
+            }
+        }
+    }
+
+    private void prepare(Region region) {
+        this.removeEntities(region);
+        // empty containers first, otherwise replacing them would drop their contents
+        for(BlockState state : this.blockEntities(this.play, region, false)) {
+            if(state instanceof Container container) container.getInventory().clear();
+        }
+    }
+
+    private void copyBlock(int x, int y, int z) {
+        BlockData source = this.template.getBlockAt(x, y, z).getBlockData();
+        Block target = this.play.getBlockAt(x, y, z);
+        if(!target.getBlockData().equals(source)) target.setBlockData(source, false);
+    }
+
+    private void finish(Region region) {
+        for(BlockState state : this.blockEntities(this.template, region, true)) {
+            state.copy(new Location(this.play, state.getX(), state.getY(), state.getZ())).update(true, false);
+        }
+        this.removeEntities(region);
+    }
+
+    private List<BlockState> blockEntities(World world, Region region, boolean snapshot) {
+        List<BlockState> states = new ArrayList<>();
+        for(int cx = region.minChunkX(); cx <= region.maxChunkX(); cx++) {
+            for(int cz = region.minChunkZ(); cz <= region.maxChunkZ(); cz++) {
+                Chunk chunk = world.getChunkAt(cx, cz);
+                for(BlockState state : chunk.getTileEntities(snapshot)) {
+                    if(region.contains(state.getX(), state.getY(), state.getZ())) states.add(state);
+                }
+            }
+        }
+        return states;
+    }
+
+    private void removeEntities(Region region) {
+        BoundingBox box = new BoundingBox(
+            region.minX(), region.minY(), region.minZ(),
+            region.maxX() + 1, region.maxY() + 1, region.maxZ() + 1
+        );
+        for(Entity entity : this.play.getNearbyEntities(box)) {
+            if(entity instanceof Player) continue;
+            if(entity.getScoreboardTags().contains(Displays.MANAGED_TAG)) continue;
+            entity.remove();
+        }
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ArenaSettings.java

@@ -0,0 +1,94 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import eu.mhsl.craftattack.spawn.core.config.ConfigUtil;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.configuration.ConfigurationSection;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Positions and limits from the {@code arena} config section. All positions refer to the play world,
+ * no matter which world was stored.
+ */
+record ArenaSettings(
+    @Nullable Location tribuneSpawn,
+    @Nullable Region syncRegion,
+    @Nullable Region[] pads,
+    List<Slot> arenas,
+    int fightSeconds,
+    int countdownSeconds,
+    int resetBlocksPerTick,
+    String returnServer
+) {
+    static final String[] PAD_KEYS = {"red", "blue"};
+
+    record Slot(String name, @Nullable Region region, @Nullable Location[] spawns, @Nullable Location display) {
+        boolean isComplete() {
+            return this.region != null && this.spawns[0] != null && this.spawns[1] != null;
+        }
+
+        Location displayLocation(World world) {
+            if(this.display != null) return this.display;
+            return new Location(world, this.region.centerX(), this.region.maxY() + 1.5, this.region.centerZ());
+        }
+    }
+
+    static ArenaSettings read(ConfigurationSection config, World world) {
+        Region[] pads = new Region[PAD_KEYS.length];
+        for(int i = 0; i < PAD_KEYS.length; i++) {
+            pads[i] = readRegion(config.getConfigurationSection("pads." + PAD_KEYS[i]));
+        }
+
+        List<Slot> arenas = new ArrayList<>();
+        ConfigurationSection arenaSection = config.getConfigurationSection("arenas");
+        if(arenaSection != null) {
+            for(String name : arenaSection.getKeys(false)) {
+                ConfigurationSection slot = arenaSection.getConfigurationSection(name);
+                if(slot == null) continue;
+                arenas.add(new Slot(
+                    name,
+                    readRegion(slot.getConfigurationSection("region")),
+                    new Location[]{
+                        readLocation(slot.getConfigurationSection("spawn1"), world),
+                        readLocation(slot.getConfigurationSection("spawn2"), world)
+                    },
+                    readLocation(slot.getConfigurationSection("display"), world)
+                ));
+            }
+        }
+
+        return new ArenaSettings(
+            readLocation(config.getConfigurationSection("tribuneSpawn"), world),
+            readRegion(config.getConfigurationSection("syncRegion")),
+            pads,
+            arenas,
+            Math.max(1, config.getInt("fightMinutes", 10)) * 60,
+            Math.max(1, config.getInt("countdownSeconds", 5)),
+            Math.max(1000, config.getInt("resetBlocksPerTick", 20000)),
+            config.getString("connect-server-name", "craftattack")
+        );
+    }
+
+    boolean padsComplete() {
+        return this.pads[0] != null && this.pads[1] != null;
+    }
+
+    private static @Nullable Region readRegion(@Nullable ConfigurationSection section) {
+        if(section == null) return null;
+        List<Integer> a = section.getIntegerList("pos1");
+        List<Integer> b = section.getIntegerList("pos2");
+        if(a.size() != 3 || b.size() != 3) return null;
+        return Region.of(a.get(0), a.get(1), a.get(2), b.get(0), b.get(1), b.get(2));
+    }
+
+    private static @Nullable Location readLocation(@Nullable ConfigurationSection section, World world) {
+        if(section == null) return null;
+        Location location = ConfigUtil.Position.paseLocation(section);
+        location.setWorld(world);
+        return location;
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ArenaSetupCommand.java

@@ -0,0 +1,116 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceCommand;
+import eu.mhsl.craftattack.spawn.core.config.ConfigUtil;
+import eu.mhsl.craftattack.spawn.core.config.Configuration;
+import org.bukkit.Location;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.configuration.ConfigurationSection;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Setting up tribune, pads and arenas at the own position. Works in the play world and in the template.
+ * Changes take effect with {@code /arenasetup reload}.
+ */
+class ArenaSetupCommand extends ApplianceCommand.PlayerChecked<Arena> {
+    private static final String USAGE = String.join("\n",
+        "/arenasetup tribune",
+        "/arenasetup villager",
+        "/arenasetup pad <red|blue> <pos1|pos2>",
+        "/arenasetup arena <name> <pos1|pos2|spawn1|spawn2|display|remove>",
+        "/arenasetup syncregion <pos1|pos2>",
+        "/arenasetup sync",
+        "/arenasetup reload"
+    );
+
+    ArenaSetupCommand() {
+        super("arenasetup");
+    }
+
+    @Override
+    public @Nullable String permission() {
+        return "admin";
+    }
+
+    @Override
+    protected void execute(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+        if(args.length == 0) throw new Error("\n" + USAGE);
+        Location location = this.getPlayer().getLocation().clone();
+        location.setWorld(this.getAppliance().worlds().play());
+        ConfigurationSection config = this.getAppliance().localConfig();
+
+        switch(args[0]) {
+            case "tribune" -> this.writeLocation(config, "tribuneSpawn", location);
+            case "villager" -> this.getAppliance().moveVillager(location);
+            case "pad" -> {
+                if(args.length < 3 || !List.of(ArenaSettings.PAD_KEYS).contains(args[1])) throw new Error(USAGE);
+                this.writeCorner(config, "pads." + args[1], args[2], location);
+            }
+            case "arena" -> {
+                if(args.length < 3) throw new Error(USAGE);
+                String path = "arenas." + args[1];
+                switch(args[2]) {
+                    case "pos1", "pos2" -> this.writeCorner(config, path + ".region", args[2], location);
+                    case "spawn1", "spawn2", "display" -> this.writeLocation(config, path + "." + args[2], location);
+                    case "remove" -> config.set(path, null);
+                    default -> throw new Error(USAGE);
+                }
+            }
+            case "syncregion" -> {
+                if(args.length < 2) throw new Error(USAGE);
+                this.writeCorner(config, "syncRegion", args[1], location);
+            }
+            case "sync" -> {
+                if(this.getAppliance().isBusy()) throw new Error("Es läuft gerade ein Kampf, Countdown oder Reset");
+                this.getAppliance().syncAll();
+                sender.sendMessage(Style.message("Die Spielwelt wird aus der Vorlage übernommen."));
+                return;
+            }
+            case "reload" -> {
+                this.getAppliance().reload();
+                sender.sendMessage(Style.message("Einstellungen übernommen. Die Arenen werden aus der Vorlage aufgebaut."));
+                return;
+            }
+            default -> throw new Error("\n" + USAGE);
+        }
+
+        Configuration.saveChanges();
+        sender.sendMessage(Style.message("Gespeichert. Mit /arenasetup reload übernehmen."));
+    }
+
+    private void writeCorner(ConfigurationSection config, String path, String corner, Location location) {
+        if(!corner.equals("pos1") && !corner.equals("pos2")) throw new Error(USAGE);
+        config.set(path + "." + corner, List.of(location.getBlockX(), location.getBlockY(), location.getBlockZ()));
+    }
+
+    private void writeLocation(ConfigurationSection config, String path, Location location) {
+        ConfigurationSection section = Optional.ofNullable(config.getConfigurationSection(path)).orElseGet(() -> config.createSection(path));
+        ConfigUtil.Position.writeLocation(section, location);
+    }
+
+    @Override
+    public @Nullable List<String> onTabComplete(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+        List<String> options = switch(args.length) {
+            case 1 -> List.of("tribune", "villager", "pad", "arena", "syncregion", "sync", "reload");
+            case 2 -> switch(args[0]) {
+                case "pad" -> Arrays.asList(ArenaSettings.PAD_KEYS);
+                case "syncregion" -> List.of("pos1", "pos2");
+                case "arena" -> this.getAppliance().arenaNames();
+                default -> List.of();
+            };
+            case 3 -> switch(args[0]) {
+                case "pad" -> List.of("pos1", "pos2");
+                case "arena" -> List.of("pos1", "pos2", "spawn1", "spawn2", "display", "remove");
+                default -> List.of();
+            };
+            default -> List.of();
+        };
+        return this.tabCompleteReducer(options, args);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ArenaSlot.java

@@ -0,0 +1,44 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import org.bukkit.World;
+import org.bukkit.entity.TextDisplay;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * One arena: free, in a fight or being reset.
+ */
+final class ArenaSlot {
+    enum State {
+        FREE,
+        FIGHT,
+        RESET
+    }
+
+    final ArenaSettings.Slot settings;
+    State state = State.RESET;
+    @Nullable Fight fight;
+    private final TextDisplay display;
+
+    ArenaSlot(ArenaSettings.Slot settings, World world) {
+        this.settings = settings;
+        this.display = Displays.spawn(settings.displayLocation(world));
+    }
+
+    void updateDisplay() {
+        Component title = Component.text("Arena " + this.settings.name(), NamedTextColor.GOLD);
+        Component status = switch(this.state) {
+            case FREE -> Component.text("Frei", NamedTextColor.GREEN);
+            case RESET -> Component.text("Wird zurückgesetzt", NamedTextColor.YELLOW);
+            case FIGHT -> this.fight == null
+                ? Component.text("Kampf", NamedTextColor.RED)
+                : this.fight.headline().appendNewline().append(Component.text(Style.time(this.fight.secondsLeft()), NamedTextColor.WHITE));
+        };
+        this.display.text(title.appendNewline().append(status));
+    }
+
+    void remove() {
+        this.display.remove();
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ArenaWorlds.java

@@ -0,0 +1,89 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import org.bukkit.Bukkit;
+import org.bukkit.GameRules;
+import org.bukkit.World;
+import org.bukkit.WorldCreator;
+import org.bukkit.generator.ChunkGenerator;
+import org.bukkit.plugin.Plugin;
+
+import java.util.Objects;
+
+/**
+ * The play world and its template. Players only fight in the play world; admins build in the template,
+ * which is copied over the play world on every reset.
+ */
+final class ArenaWorlds {
+    static final String PLAY = "arena";
+    static final String TEMPLATE = "arena_template";
+
+    private static final class VoidGenerator extends ChunkGenerator {
+    }
+
+    private final World play;
+    private final World template;
+
+    ArenaWorlds() {
+        this.play = load(PLAY);
+        this.template = load(TEMPLATE);
+
+        for(World world : new World[]{this.play, this.template}) {
+            world.setGameRule(GameRules.ADVANCE_TIME, false);
+            world.setGameRule(GameRules.ADVANCE_WEATHER, false);
+            world.setGameRule(GameRules.SPAWN_MOBS, false);
+            world.setGameRule(GameRules.SPAWN_MONSTERS, false);
+            world.setGameRule(GameRules.SPAWN_PHANTOMS, false);
+            world.setGameRule(GameRules.SPAWN_PATROLS, false);
+            world.setGameRule(GameRules.SPAWN_WANDERING_TRADERS, false);
+            world.setGameRule(GameRules.SPAWN_WARDENS, false);
+            world.setGameRule(GameRules.RAIDS, false);
+            world.setGameRule(GameRules.SHOW_DEATH_MESSAGES, false);
+            world.setStorm(false);
+            world.setThundering(false);
+            world.setTime(6000);
+        }
+        this.play.setGameRule(GameRules.IMMEDIATE_RESPAWN, true);
+        this.play.setGameRule(GameRules.KEEP_INVENTORY, true);
+        this.template.setGameRule(GameRules.RANDOM_TICK_SPEED, 0);
+        this.template.setGameRule(GameRules.FIRE_SPREAD_RADIUS_AROUND_PLAYER, 0);
+    }
+
+    private static World load(String name) {
+        World world = Bukkit.getWorld(name);
+        if(world != null) return world;
+        return Objects.requireNonNull(
+            new WorldCreator(name).generator(new VoidGenerator()).generateStructures(false).createWorld(),
+            "Could not create world " + name
+        );
+    }
+
+    World play() {
+        return this.play;
+    }
+
+    World template() {
+        return this.template;
+    }
+
+    boolean isPlay(World world) {
+        return this.play.equals(world);
+    }
+
+    /**
+     * Keeps all chunks of the region loaded in both worlds, so resets never wait for chunk loading.
+     */
+    void keepLoaded(Region region, Plugin plugin) {
+        for(int cx = region.minChunkX(); cx <= region.maxChunkX(); cx++) {
+            for(int cz = region.minChunkZ(); cz <= region.maxChunkZ(); cz++) {
+                this.play.addPluginChunkTicket(cx, cz, plugin);
+                this.template.addPluginChunkTicket(cx, cz, plugin);
+            }
+        }
+    }
+
+    void releaseChunks(Plugin plugin) {
+        this.play.removePluginChunkTickets(plugin);
+        this.template.removePluginChunkTickets(plugin);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/BuildCommand.java

@@ -0,0 +1,26 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceCommand;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Switches between the play world and the template at the same position.
+ */
+class BuildCommand extends ApplianceCommand.PlayerChecked<Arena> {
+    BuildCommand() {
+        super("build");
+    }
+
+    @Override
+    public @Nullable String permission() {
+        return "arena.build";
+    }
+
+    @Override
+    protected void execute(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+        this.getAppliance().toggleBuild(this.getPlayer());
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/CraftAttackCommand.java

@@ -0,0 +1,17 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceCommand;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.jetbrains.annotations.NotNull;
+
+class CraftAttackCommand extends ApplianceCommand.PlayerChecked<Arena> {
+    CraftAttackCommand() {
+        super("craftattack");
+    }
+
+    @Override
+    protected void execute(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+        this.getAppliance().sendToCraftAttack(this.getPlayer());
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Displays.java

@@ -0,0 +1,31 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.Main;
+import org.bukkit.Color;
+import org.bukkit.Location;
+import org.bukkit.entity.Display;
+import org.bukkit.entity.TextDisplay;
+
+/**
+ * Floating texts above pads and arenas. They are not saved with the world and come back with every start.
+ */
+final class Displays {
+    static final String MANAGED_TAG = "arena_managed";
+
+    private Displays() {
+    }
+
+    static TextDisplay spawn(Location location) {
+        // displays are not saved, they would vanish with an unloaded chunk
+        location.getWorld().addPluginChunkTicket(location.getBlockX() >> 4, location.getBlockZ() >> 4, Main.instance());
+        return location.getWorld().spawn(location, TextDisplay.class, display -> {
+            display.setPersistent(false);
+            display.setBillboard(Display.Billboard.CENTER);
+            display.setAlignment(TextDisplay.TextAlignment.CENTER);
+            display.setShadowed(true);
+            display.setBackgroundColor(Color.fromARGB(110, 0, 0, 0));
+            display.setLineWidth(220);
+            display.addScoreboardTag(MANAGED_TAG);
+        });
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Fight.java

@@ -0,0 +1,292 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode;
+import eu.mhsl.craftattack.spawn.core.Main;
+import net.kyori.adventure.bossbar.BossBar;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.title.Title;
+import org.bukkit.Bukkit;
+import org.bukkit.Color;
+import org.bukkit.GameMode;
+import org.bukkit.Location;
+import org.bukkit.Particle;
+import org.bukkit.Sound;
+import org.bukkit.entity.Player;
+import org.bukkit.scheduler.BukkitTask;
+import org.jetbrains.annotations.Nullable;
+
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+
+/**
+ * A running fight in one arena. Fighter 0 comes from the red pad and uses spawn 1, fighter 1 the blue pad and spawn 2.
+ */
+final class Fight {
+    private static final int CELEBRATION_TICKS = 60;
+    private static final double SPECTATOR_RANGE = 24;
+
+    private final Arena arena;
+    private final ArenaSlot slot;
+    private final UUID[] fighters;
+    private final String[] names;
+    private final UUID challenger;
+    private final FightMode mode;
+    private final BossBar bossBar;
+    private final Set<UUID> bossBarViewers = new HashSet<>();
+    private int secondsLeft;
+    private boolean over;
+    private @Nullable BukkitTask timer;
+
+    Fight(Arena arena, ArenaSlot slot, Player red, Player blue, UUID challenger, FightMode mode) {
+        this.arena = arena;
+        this.slot = slot;
+        this.fighters = new UUID[]{red.getUniqueId(), blue.getUniqueId()};
+        this.names = new String[]{red.getName(), blue.getName()};
+        this.challenger = challenger;
+        this.mode = mode;
+        this.secondsLeft = arena.settings().fightSeconds();
+        this.bossBar = BossBar.bossBar(Component.empty(), 1f, BossBar.Color.RED, BossBar.Overlay.NOTCHED_10);
+    }
+
+    void start() {
+        this.slot.state = ArenaSlot.State.FIGHT;
+        this.slot.fight = this;
+
+        FightMode.Role[] roles = new FightMode.Role[2];
+        for(int i = 0; i < 2; i++) {
+            roles[i] = this.fighters[i].equals(this.challenger) ? FightMode.Role.CHALLENGER : FightMode.Role.OPPONENT;
+        }
+        UUID challengerId = this.challenger;
+        UUID opponentId = this.fighters[0].equals(challengerId) ? this.fighters[1] : this.fighters[0];
+
+        for(int i = 0; i < 2; i++) {
+            Player player = Bukkit.getPlayer(this.fighters[i]);
+            if(player == null) continue;
+            UUID kitOwner = this.mode.kitSource(roles[i]) == FightMode.Role.CHALLENGER ? challengerId : opponentId;
+
+            this.arena.setState(player, Arena.PlayerState.FIGHT);
+            this.arena.teams().join(player, Teams.fight(i));
+            player.closeInventory();
+            player.teleport(this.slot.settings.spawns()[i]);
+            Arena.restore(player, GameMode.SURVIVAL);
+            InventoryStore.apply(player, kitOwner);
+
+            player.showTitle(Title.title(
+                Component.text("Kampf!", NamedTextColor.GOLD),
+                Component.text("gegen ", NamedTextColor.GRAY).append(Component.text(this.names[1 - i], Style.PAD_TEXT_COLORS[1 - i])),
+                Title.Times.times(Duration.ZERO, Duration.ofMillis(1500), Duration.ofMillis(500))
+            ));
+            Style.play(player, Sound.EVENT_RAID_HORN, 1.2f);
+        }
+
+        Bukkit.broadcast(Style.message(
+            this.headline().append(Component.text(" in Arena " + this.slot.settings.name() + ". Modus: " + this.mode.displayName(), NamedTextColor.GRAY))
+        ));
+        this.updateBossBar();
+        this.timer = Bukkit.getScheduler().runTaskTimer(Main.instance(), this::tickSecond, 20, 20);
+    }
+
+    Component headline() {
+        return Component.text(this.names[0], Style.PAD_TEXT_COLORS[0])
+            .append(Component.text(" gegen ", NamedTextColor.GRAY))
+            .append(Component.text(this.names[1], Style.PAD_TEXT_COLORS[1]));
+    }
+
+    int secondsLeft() {
+        return this.secondsLeft;
+    }
+
+    boolean isOver() {
+        return this.over;
+    }
+
+    boolean involves(UUID player) {
+        return this.fighters[0].equals(player) || this.fighters[1].equals(player);
+    }
+
+    ArenaSlot slot() {
+        return this.slot;
+    }
+
+    private void tickSecond() {
+        if(this.over) return;
+        if(--this.secondsLeft <= 0) {
+            this.finish(-1, Component.text("Die Zeit ist abgelaufen.", NamedTextColor.GRAY));
+            return;
+        }
+        if(this.secondsLeft == 60 || this.secondsLeft == 10) {
+            this.fighterPlayers().forEach(player -> {
+                player.sendActionBar(Component.text("Noch " + this.secondsLeft + " Sekunden", NamedTextColor.YELLOW));
+                Style.play(player, Sound.BLOCK_NOTE_BLOCK_HAT, 0.8f);
+            });
+        }
+        this.updateBossBar();
+    }
+
+    private void updateBossBar() {
+        this.bossBar.name(this.headline().append(Component.text("   " + Style.time(this.secondsLeft), NamedTextColor.WHITE)));
+        this.bossBar.progress(Math.clamp((float) this.secondsLeft / this.arena.settings().fightSeconds(), 0f, 1f));
+
+        Set<UUID> viewers = new HashSet<>();
+        for(Player player : this.arena.worlds().play().getPlayers()) {
+            if(this.involves(player.getUniqueId()) || this.isSpectating(player)) viewers.add(player.getUniqueId());
+        }
+        for(UUID uuid : this.bossBarViewers) {
+            Player player = Bukkit.getPlayer(uuid);
+            if(player != null && !viewers.contains(uuid)) player.hideBossBar(this.bossBar);
+        }
+        for(UUID uuid : viewers) {
+            Player player = Bukkit.getPlayer(uuid);
+            if(player != null) player.showBossBar(this.bossBar);
+        }
+        this.bossBarViewers.clear();
+        this.bossBarViewers.addAll(viewers);
+    }
+
+    private boolean isSpectating(Player player) {
+        if(this.arena.state(player) != Arena.PlayerState.TRIBUNE && this.arena.state(player) != Arena.PlayerState.PAD) return false;
+        var region = this.slot.settings.region();
+        double dx = Math.max(0, Math.max(region.minX() - player.getX(), player.getX() - (region.maxX() + 1)));
+        double dz = Math.max(0, Math.max(region.minZ() - player.getZ(), player.getZ() - (region.maxZ() + 1)));
+        return Math.hypot(dx, dz) <= SPECTATOR_RANGE;
+    }
+
+    /**
+     * The player took lethal damage.
+     */
+    void defeated(Player loser) {
+        int index = this.indexOf(loser.getUniqueId());
+        if(index == -1 || this.over) return;
+        Player winner = Bukkit.getPlayer(this.fighters[1 - index]);
+        Component detail = winner == null
+            ? Component.empty()
+            : Component.text("(" + this.mode.displayName() + ", " + Style.hearts(winner.getHealth() + winner.getAbsorptionAmount()) + " ❤ übrig)", NamedTextColor.GRAY);
+        this.finish(1 - index, detail);
+    }
+
+    /**
+     * The player left the server during the fight.
+     */
+    void forfeit(UUID quitter) {
+        int index = this.indexOf(quitter);
+        if(index == -1 || this.over) return;
+        this.finish(1 - index, Component.text("(" + this.names[index] + " hat die Arena verlassen)", NamedTextColor.GRAY));
+    }
+
+    /**
+     * Ends the fight without a winner and without celebration, for example on shutdown.
+     */
+    void abort() {
+        if(this.over) return;
+        this.over = true;
+        this.stopTimer();
+        this.hideBossBar();
+        this.fighterPlayers().forEach(this.arena::toTribune);
+        this.slot.fight = null;
+    }
+
+    private void finish(int winnerIndex, Component detail) {
+        this.over = true;
+        this.stopTimer();
+
+        if(winnerIndex == -1) {
+            Bukkit.broadcast(Style.message(
+                Component.text(this.names[0], Style.PAD_TEXT_COLORS[0])
+                    .append(Component.text(" und ", NamedTextColor.GRAY))
+                    .append(Component.text(this.names[1], Style.PAD_TEXT_COLORS[1]))
+                    .append(Component.text(" trennen sich unentschieden. ", NamedTextColor.GRAY))
+                    .append(detail)
+            ));
+            this.fighterPlayers().forEach(player -> {
+                player.showTitle(Title.title(Component.text("Unentschieden", NamedTextColor.YELLOW), detail));
+                Style.play(player, Sound.BLOCK_BEACON_DEACTIVATE, 1f);
+                this.arena.toTribune(player);
+            });
+            this.afterCelebration();
+            return;
+        }
+
+        int loserIndex = 1 - winnerIndex;
+        Bukkit.broadcast(Style.message(
+            Component.text(this.names[winnerIndex], Style.PAD_TEXT_COLORS[winnerIndex])
+                .append(Component.text(" hat gegen ", NamedTextColor.GRAY))
+                .append(Component.text(this.names[loserIndex], Style.PAD_TEXT_COLORS[loserIndex]))
+                .append(Component.text(" gewonnen ", NamedTextColor.GRAY))
+                .append(detail)
+        ));
+
+        Player loser = Bukkit.getPlayer(this.fighters[loserIndex]);
+        if(loser != null) {
+            loser.showTitle(Title.title(
+                Component.text("Verloren", NamedTextColor.RED),
+                Component.text(this.names[winnerIndex] + " hat gewonnen", NamedTextColor.GRAY)
+            ));
+            Style.play(loser, Sound.BLOCK_BEACON_DEACTIVATE, 1f);
+            this.arena.toTribune(loser);
+        }
+
+        Player winner = Bukkit.getPlayer(this.fighters[winnerIndex]);
+        if(winner != null) {
+            winner.showTitle(Title.title(
+                Component.text("Gewonnen!", NamedTextColor.GOLD),
+                Component.text("gegen " + this.names[loserIndex], NamedTextColor.GRAY)
+            ));
+            Style.play(winner, Sound.UI_TOAST_CHALLENGE_COMPLETE, 1f);
+            this.celebrate(winner.getLocation(), Style.PAD_PARTICLE_COLORS[winnerIndex]);
+        }
+        this.afterCelebration();
+    }
+
+    private void celebrate(Location location, Color color) {
+        Location top = location.clone().add(0, 2.2, 0);
+        Particle.FIREWORK.builder().location(top).count(40).offset(0.6, 0.6, 0.6).extra(0.15).receivers(64).spawn();
+        Particle.DUST.builder().location(top).count(60).offset(1, 1, 1).data(new Particle.DustOptions(color, 1.6f)).receivers(64).spawn();
+        Style.play(top, Sound.ENTITY_FIREWORK_ROCKET_TWINKLE, 2f, 1f);
+        Style.play(top, Sound.ENTITY_FIREWORK_ROCKET_LARGE_BLAST, 2f, 1f);
+    }
+
+    private void hideBossBar() {
+        this.bossBarViewers.forEach(uuid -> {
+            Player player = Bukkit.getPlayer(uuid);
+            if(player != null) player.hideBossBar(this.bossBar);
+        });
+        this.bossBarViewers.clear();
+    }
+
+    private void afterCelebration() {
+        this.hideBossBar();
+        Bukkit.getScheduler().runTaskLater(Main.instance(), () -> {
+            for(UUID uuid : this.fighters) {
+                Player player = Bukkit.getPlayer(uuid);
+                if(player != null && this.arena.fightOf(player) == this) this.arena.toTribune(player);
+            }
+            this.slot.fight = null;
+            this.arena.resetSlot(this.slot);
+        }, CELEBRATION_TICKS);
+    }
+
+    private void stopTimer() {
+        if(this.timer != null) this.timer.cancel();
+        this.timer = null;
+    }
+
+    private int indexOf(UUID player) {
+        if(this.fighters[0].equals(player)) return 0;
+        if(this.fighters[1].equals(player)) return 1;
+        return -1;
+    }
+
+    private List<Player> fighterPlayers() {
+        List<Player> players = new ArrayList<>();
+        for(UUID uuid : this.fighters) {
+            Player player = Bukkit.getPlayer(uuid);
+            if(player != null) players.add(player);
+        }
+        return players;
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/FightListener.java

@@ -0,0 +1,93 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import eu.mhsl.craftattack.spawn.core.Main;
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import io.papermc.paper.datacomponent.DataComponentTypes;
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.entity.Projectile;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.entity.EntityDamageByEntityEvent;
+import org.bukkit.event.entity.EntityDamageEvent;
+import org.bukkit.event.entity.PlayerDeathEvent;
+import org.bukkit.event.player.PlayerRespawnEvent;
+import org.bukkit.event.player.PlayerTeleportEvent;
+import org.bukkit.inventory.ItemStack;
+
+/**
+ * Lethal damage ends the fight instead of killing the player. Totems still work as usual.
+ */
+class FightListener extends ApplianceListener<Arena> {
+    private boolean isFighting(Player player) {
+        Fight fight = this.getAppliance().fightOf(player);
+        return fight != null && !fight.isOver() && this.getAppliance().state(player) == Arena.PlayerState.FIGHT;
+    }
+
+    @EventHandler(priority = EventPriority.HIGH, ignoreCancelled = true)
+    public void onDamageByPlayer(EntityDamageByEntityEvent event) {
+        if(!(event.getEntity() instanceof Player)) return;
+        Player attacker = switch(event.getDamager()) {
+            case Player player -> player;
+            case Projectile projectile when projectile.getShooter() instanceof Player shooter -> shooter;
+            default -> null;
+        };
+        if(attacker == null || attacker == event.getEntity()) return;
+        if(!this.isFighting(attacker)) event.setCancelled(true);
+    }
+
+    @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
+    public void onDamage(EntityDamageEvent event) {
+        if(!(event.getEntity() instanceof Player player)) return;
+        if(this.getAppliance().state(player) != Arena.PlayerState.FIGHT) return;
+        Fight fight = this.getAppliance().fightOf(player);
+        if(fight == null || fight.isOver()) {
+            event.setCancelled(true);
+            return;
+        }
+        if(event.getFinalDamage() < player.getHealth()) return;
+        if(this.hasDeathProtection(player.getInventory().getItemInMainHand())
+            || this.hasDeathProtection(player.getInventory().getItemInOffHand())) return;
+
+        event.setCancelled(true);
+        fight.defeated(player);
+    }
+
+    private boolean hasDeathProtection(ItemStack item) {
+        return !item.isEmpty() && item.hasData(DataComponentTypes.DEATH_PROTECTION);
+    }
+
+    /**
+     * Safety net if a death gets through anyway: nothing drops and the fight ends.
+     */
+    @EventHandler
+    public void onDeath(PlayerDeathEvent event) {
+        event.setKeepInventory(true);
+        event.getDrops().clear();
+        event.setKeepLevel(true);
+        event.setDroppedExp(0);
+        event.deathMessage(null);
+        Fight fight = this.getAppliance().fightOf(event.getPlayer());
+        if(fight != null) fight.defeated(event.getPlayer());
+    }
+
+    @EventHandler
+    public void onRespawn(PlayerRespawnEvent event) {
+        Bukkit.getScheduler().runTask(Main.instance(), () -> this.getAppliance().toTribune(event.getPlayer()));
+    }
+
+    /**
+     * Ender pearls and chorus fruits must not leave the arena.
+     */
+    @EventHandler(ignoreCancelled = true)
+    public void onTeleport(PlayerTeleportEvent event) {
+        if(event.getCause() == PlayerTeleportEvent.TeleportCause.PLUGIN || event.getCause() == PlayerTeleportEvent.TeleportCause.COMMAND) return;
+        if(this.getAppliance().state(event.getPlayer()) != Arena.PlayerState.FIGHT) return;
+        Region region = this.getAppliance().arenaRegionOf(event.getPlayer());
+        if(region == null) return;
+        if(event.getTo().getWorld() != event.getFrom().getWorld() || !region.contains(event.getTo().getX(), event.getTo().getY(), event.getTo().getZ())) {
+            event.setCancelled(true);
+        }
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/InventoryStore.java

@@ -0,0 +1,43 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Inventory copies sent by the main server. Kept in memory only: after a restart of the arena server
+ * players arrive with an empty inventory until they come over again.
+ */
+final class InventoryStore {
+    static final int MAX_BYTES = 16 * 1024 * 1024;
+    private static final Map<UUID, byte[]> snapshots = new ConcurrentHashMap<>();
+
+    private InventoryStore() {
+    }
+
+    static void put(UUID player, byte[] serializedItems) {
+        if(serializedItems.length > MAX_BYTES) throw new IllegalArgumentException("Inventory too large");
+        snapshots.put(player, serializedItems);
+    }
+
+    /**
+     * @return a fresh copy of the player's inventory, empty if none was sent
+     */
+    static ItemStack[] get(UUID player) {
+        byte[] bytes = snapshots.get(player);
+        if(bytes == null) return new ItemStack[0];
+        return ItemStack.deserializeItemsFromBytes(bytes);
+    }
+
+    static void apply(Player player, UUID source) {
+        ItemStack[] items = get(source);
+        int size = player.getInventory().getSize();
+        ItemStack[] contents = new ItemStack[size];
+        System.arraycopy(items, 0, contents, 0, Math.min(items.length, size));
+        player.getInventory().setContents(contents);
+        player.setItemOnCursor(null);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Lobby.java

@@ -0,0 +1,299 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode;
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.PadLobby;
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.Region;
+import eu.mhsl.craftattack.spawn.core.util.world.InteractSounds;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.title.Title;
+import org.bukkit.Bukkit;
+import org.bukkit.Color;
+import org.bukkit.Location;
+import org.bukkit.Particle;
+import org.bukkit.Sound;
+import org.bukkit.entity.Player;
+import org.bukkit.entity.TextDisplay;
+import org.bukkit.util.Vector;
+import org.jetbrains.annotations.Nullable;
+
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+
+/**
+ * The two start pads in the world: who stands where, pushing others away from taken pads,
+ * inventories, countdown, texts, particles and sounds. The rules themselves live in {@link PadLobby}.
+ */
+final class Lobby implements PadLobby.Listener {
+    /** How far around a taken pad other players get pushed away. */
+    private static final double PUSH_MARGIN = 0.4;
+
+    private final Arena arena;
+    private final Region[] regions;
+    private final PadLobby pads;
+    private final TextDisplay[] displays = new TextDisplay[PadLobby.PADS];
+    private final Map<UUID, Long> lastPushSound = new HashMap<>();
+    private long ticks;
+
+    Lobby(Arena arena, Region[] regions) {
+        this.arena = arena;
+        this.regions = regions;
+        this.pads = new PadLobby(this, arena.settings().countdownSeconds());
+        for(int i = 0; i < PadLobby.PADS; i++) {
+            Region region = regions[i];
+            this.displays[i] = Displays.spawn(new Location(arena.worlds().play(), region.centerX(), region.maxY() + 2.6, region.centerZ()));
+        }
+    }
+
+    void tick() {
+        this.ticks++;
+        for(Player player : this.arena.worlds().play().getPlayers()) {
+            Arena.PlayerState state = this.arena.state(player);
+            if(state == Arena.PlayerState.PAD) this.checkLeave(player);
+            else if(state == Arena.PlayerState.TRIBUNE) this.checkEnter(player);
+        }
+
+        this.pads.tick(this.arena.hasFreeSlot());
+
+        if(this.ticks % 3 == 0) this.drawParticles();
+        if(this.ticks % 5 == 0) this.updateDisplays();
+    }
+
+    private void checkLeave(Player player) {
+        int pad = this.pads.padOf(player.getUniqueId());
+        if(pad != -1 && this.isOn(player, pad, 0)) return;
+        this.leave(player);
+    }
+
+    private void checkEnter(Player player) {
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            if(this.pads.occupant(pad) != null) {
+                if(this.isOn(player, pad, PUSH_MARGIN)) this.pushAway(player, pad);
+                continue;
+            }
+            if(!this.isOn(player, pad, 0)) continue;
+            if(!this.pads.enter(pad, player.getUniqueId())) continue;
+
+            this.arena.setState(player, Arena.PlayerState.PAD);
+            this.arena.teams().join(player, Teams.pad(pad));
+            Style.play(player, Sound.BLOCK_NOTE_BLOCK_PLING, 1.4f);
+            return;
+        }
+    }
+
+    /**
+     * Removes the player from the pad, if standing on one.
+     */
+    void leave(Player player) {
+        if(this.pads.padOf(player.getUniqueId()) == -1) return;
+        this.pads.leave(player.getUniqueId());
+        if(ModeMenu.isOpen(player)) player.closeInventory();
+        this.arena.teams().leave(player);
+        this.arena.setState(player, Arena.PlayerState.TRIBUNE);
+    }
+
+    void chooseMode(Player player, FightMode mode) {
+        if(!this.pads.setMode(player.getUniqueId(), mode)) {
+            player.closeInventory();
+            return;
+        }
+        InteractSounds.of(player).click();
+        player.closeInventory();
+        player.sendActionBar(Component.text("Modus: " + mode.displayName(), NamedTextColor.GOLD));
+    }
+
+    boolean isIdle() {
+        return this.pads.isIdle();
+    }
+
+    void shutdown() {
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            UUID occupant = this.pads.occupant(pad);
+            Player player = occupant == null ? null : Bukkit.getPlayer(occupant);
+            if(player != null) this.leave(player);
+        }
+        for(TextDisplay display : this.displays) display.remove();
+    }
+
+    private boolean isOn(Player player, int pad, double margin) {
+        Region region = this.regions[pad];
+        return player.getX() >= region.minX() - margin && player.getX() < region.maxX() + 1 + margin
+            && player.getZ() >= region.minZ() - margin && player.getZ() < region.maxZ() + 1 + margin
+            && player.getY() >= region.minY() - 0.5 && player.getY() < region.maxY() + 2;
+    }
+
+    private void pushAway(Player player, int pad) {
+        Region region = this.regions[pad];
+        Vector direction = new Vector(player.getX() - region.centerX(), 0, player.getZ() - region.centerZ());
+        if(direction.lengthSquared() < 0.01) direction = new Vector(1, 0, 0);
+        player.setVelocity(direction.normalize().multiply(0.6).setY(0.25));
+
+        long now = System.currentTimeMillis();
+        if(now - this.lastPushSound.getOrDefault(player.getUniqueId(), 0L) < 1000) return;
+        this.lastPushSound.put(player.getUniqueId(), now);
+        Style.play(player, Sound.BLOCK_NOTE_BLOCK_BASS, 0.6f);
+        player.sendActionBar(Component.text("Dieses Feld ist besetzt", NamedTextColor.RED));
+    }
+
+    @Override
+    public void challengerSelected(UUID challenger) {
+        Player player = Bukkit.getPlayer(challenger);
+        if(player == null) return;
+        player.sendMessage(Style.message("Du forderst heraus. Wähle den Modus. Wer sich auf das andere Feld stellt, nimmt an."));
+        InteractSounds.of(player).open();
+        ModeMenu.open(player, this.pads.mode());
+    }
+
+    @Override
+    public void kitsApplied(UUID challenger, UUID opponent, FightMode mode) {
+        Player challengerPlayer = Bukkit.getPlayer(challenger);
+        Player opponentPlayer = Bukkit.getPlayer(opponent);
+        if(challengerPlayer == null || opponentPlayer == null) return;
+        if(ModeMenu.isOpen(challengerPlayer)) challengerPlayer.closeInventory();
+
+        InventoryStore.apply(challengerPlayer, mode.kitSource(FightMode.Role.CHALLENGER) == FightMode.Role.CHALLENGER ? challenger : opponent);
+        InventoryStore.apply(opponentPlayer, mode.kitSource(FightMode.Role.OPPONENT) == FightMode.Role.CHALLENGER ? challenger : opponent);
+
+        String kitText = switch(mode) {
+            case OWN -> "Jeder kämpft mit seinem eigenen Inventar.";
+            case CHALLENGER -> "Ihr kämpft beide mit dem Inventar von " + challengerPlayer.getName() + ".";
+            case OPPONENT -> "Ihr kämpft beide mit dem Inventar von " + opponentPlayer.getName() + ".";
+        };
+        opponentPlayer.sendMessage(Style.message("Du nimmst die Herausforderung von " + challengerPlayer.getName() + " an. " + kitText + " Verlasse das Feld, um abzubrechen."));
+        challengerPlayer.sendMessage(Style.message(opponentPlayer.getName() + " nimmt deine Herausforderung an. " + kitText + " Verlasse das Feld, um abzubrechen."));
+        for(Player player : new Player[]{challengerPlayer, opponentPlayer}) {
+            Style.play(player, Sound.ITEM_ARMOR_EQUIP_NETHERITE, 1f);
+        }
+    }
+
+    @Override
+    public void kitReverted(UUID uuid) {
+        Player player = Bukkit.getPlayer(uuid);
+        if(player != null) InventoryStore.apply(player, uuid);
+    }
+
+    @Override
+    public void countdown(int secondsLeft) {
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            Player player = this.occupantPlayer(pad);
+            Player other = this.occupantPlayer(1 - pad);
+            if(player == null || other == null) continue;
+            player.showTitle(Title.title(
+                Component.text(secondsLeft, NamedTextColor.GOLD),
+                Component.text("Kampf gegen ", NamedTextColor.GRAY).append(Component.text(other.getName(), Style.PAD_TEXT_COLORS[1 - pad])),
+                Title.Times.times(Duration.ZERO, Duration.ofMillis(1100), Duration.ZERO)
+            ));
+            Style.play(player, Sound.BLOCK_NOTE_BLOCK_PLING, 0.6f + (this.arena.settings().countdownSeconds() - secondsLeft) * 0.2f);
+        }
+    }
+
+    @Override
+    public void countdownCancelled() {
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            Player player = this.occupantPlayer(pad);
+            if(player == null) continue;
+            player.clearTitle();
+            player.sendActionBar(Component.text("Abgebrochen", NamedTextColor.RED));
+            Style.play(player, Sound.BLOCK_NOTE_BLOCK_BASS, 0.5f);
+        }
+    }
+
+    @Override
+    public void start(UUID challenger, UUID opponent, FightMode mode, int challengerPad) {
+        Player challengerPlayer = Bukkit.getPlayer(challenger);
+        Player opponentPlayer = Bukkit.getPlayer(opponent);
+        if(challengerPlayer == null || opponentPlayer == null) {
+            if(challengerPlayer != null) this.arena.toTribune(challengerPlayer);
+            if(opponentPlayer != null) this.arena.toTribune(opponentPlayer);
+            return;
+        }
+        Player red = challengerPad == 0 ? challengerPlayer : opponentPlayer;
+        Player blue = challengerPad == 0 ? opponentPlayer : challengerPlayer;
+        this.arena.startFight(red, blue, challenger, mode);
+    }
+
+    private @Nullable Player occupantPlayer(int pad) {
+        UUID occupant = this.pads.occupant(pad);
+        return occupant == null ? null : Bukkit.getPlayer(occupant);
+    }
+
+    private void updateDisplays() {
+        boolean waiting = this.pads.isFull() && !this.arena.hasFreeSlot();
+        Player challenger = this.pads.challenger() == null ? null : Bukkit.getPlayer(this.pads.challenger());
+        String modeText = "Modus: " + this.pads.mode().displayName();
+
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            Component title = Component.text(Style.PAD_NAMES[pad], Style.PAD_TEXT_COLORS[pad]);
+            Player occupant = this.occupantPlayer(pad);
+            Component body;
+            if(waiting) {
+                body = Component.text("Alle Arenen belegt", NamedTextColor.GRAY).appendNewline()
+                    .append(Component.text("Gleich geht es los", NamedTextColor.WHITE));
+            } else if(this.pads.isCountingDown()) {
+                body = Component.text(occupant == null ? "" : occupant.getName(), Style.PAD_TEXT_COLORS[pad]).appendNewline()
+                    .append(Component.text("Kampf beginnt in " + this.pads.secondsLeft(), NamedTextColor.GOLD));
+            } else if(occupant != null) {
+                body = Component.text(occupant.getName(), Style.PAD_TEXT_COLORS[pad]).appendNewline()
+                    .append(Component.text("fordert heraus", NamedTextColor.GRAY)).appendNewline()
+                    .append(Component.text(modeText, NamedTextColor.WHITE));
+            } else if(challenger != null) {
+                body = Component.text("Stell dich hierhin, um gegen", NamedTextColor.WHITE).appendNewline()
+                    .append(Component.text(challenger.getName(), Style.PAD_TEXT_COLORS[1 - pad]))
+                    .append(Component.text(" zu kämpfen", NamedTextColor.WHITE)).appendNewline()
+                    .append(Component.text(modeText, NamedTextColor.GRAY));
+            } else if(!this.arena.hasFreeSlot()) {
+                body = Component.text("Alle Arenen belegt", NamedTextColor.GRAY).appendNewline()
+                    .append(Component.text("Du kannst dich trotzdem anstellen", NamedTextColor.WHITE));
+            } else {
+                body = Component.text("Stell dich hierhin,", NamedTextColor.WHITE).appendNewline()
+                    .append(Component.text("um herauszufordern", NamedTextColor.WHITE));
+            }
+            this.displays[pad].text(title.appendNewline().append(body));
+        }
+    }
+
+    private void drawParticles() {
+        boolean waiting = this.pads.isFull() && !this.arena.hasFreeSlot();
+        boolean countdown = this.pads.isCountingDown() && !waiting;
+        for(int pad = 0; pad < PadLobby.PADS; pad++) {
+            Region region = this.regions[pad];
+            Color color = waiting ? Style.WAITING_PARTICLE_COLOR : Style.PAD_PARTICLE_COLORS[pad];
+            boolean taken = this.pads.occupant(pad) != null;
+            double spacing = countdown ? 0.25 : taken ? 0.4 : 0.6;
+            this.drawOutline(region, new Particle.DustOptions(color, taken ? 1.2f : 0.9f), spacing);
+
+            Player occupant = this.occupantPlayer(pad);
+            if(occupant == null) continue;
+            double speed = countdown ? 0.6 : 0.3;
+            for(int strand = 0; strand < 2; strand++) {
+                double angle = this.ticks * speed + strand * Math.PI;
+                double height = (this.ticks % 40) / 20.0;
+                Location point = occupant.getLocation().add(Math.cos(angle) * 0.7, height, Math.sin(angle) * 0.7);
+                Particle.DUST.builder().location(point).data(new Particle.DustOptions(color, 1f)).receivers(48).spawn();
+            }
+        }
+    }
+
+    private void drawOutline(Region region, Particle.DustOptions dust, double spacing) {
+        double y = region.minY() + 0.1;
+        double minX = region.minX();
+        double maxX = region.maxX() + 1;
+        double minZ = region.minZ();
+        double maxZ = region.maxZ() + 1;
+        Location location = new Location(this.arena.worlds().play(), 0, y, 0);
+        for(double x = minX; x <= maxX; x += spacing) {
+            this.dust(location.set(x, y, minZ), dust);
+            this.dust(location.set(x, y, maxZ), dust);
+        }
+        for(double z = minZ; z <= maxZ; z += spacing) {
+            this.dust(location.set(minX, y, z), dust);
+            this.dust(location.set(maxX, y, z), dust);
+        }
+    }
+
+    private void dust(Location location, Particle.DustOptions dust) {
+        Particle.DUST.builder().location(location).data(dust).receivers(48).spawn();
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/LockListener.java

@@ -0,0 +1,99 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.entity.EntityDamageEvent;
+import org.bukkit.event.entity.EntityPickupItemEvent;
+import org.bukkit.event.entity.EntityToggleGlideEvent;
+import org.bukkit.event.entity.FoodLevelChangeEvent;
+import org.bukkit.event.entity.ProjectileLaunchEvent;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.event.inventory.InventoryDragEvent;
+import org.bukkit.event.inventory.InventoryOpenEvent;
+import org.bukkit.event.inventory.InventoryType;
+import org.bukkit.event.player.PlayerDropItemEvent;
+import org.bukkit.event.player.PlayerInteractEvent;
+import org.bukkit.event.player.PlayerItemConsumeEvent;
+import org.bukkit.event.player.PlayerSwapHandItemsEvent;
+
+/**
+ * Outside of a fight the inventory can be looked at, but nothing can be moved, dropped or used.
+ * Nobody takes damage or gets hungry on the tribune.
+ */
+class LockListener extends ApplianceListener<Arena> {
+    private boolean isLocked(Object entity) {
+        if(!(entity instanceof Player player)) return false;
+        Arena.PlayerState state = this.getAppliance().state(player);
+        return state == Arena.PlayerState.TRIBUNE || state == Arena.PlayerState.PAD;
+    }
+
+    private void cancelIfLocked(Object entity, Cancellable event) {
+        if(this.isLocked(entity)) event.setCancelled(true);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onClick(InventoryClickEvent event) {
+        this.cancelIfLocked(event.getWhoClicked(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onDrag(InventoryDragEvent event) {
+        this.cancelIfLocked(event.getWhoClicked(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onDrop(PlayerDropItemEvent event) {
+        this.cancelIfLocked(event.getPlayer(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onSwapHands(PlayerSwapHandItemsEvent event) {
+        this.cancelIfLocked(event.getPlayer(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onInteract(PlayerInteractEvent event) {
+        this.cancelIfLocked(event.getPlayer(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onConsume(PlayerItemConsumeEvent event) {
+        this.cancelIfLocked(event.getPlayer(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onPickup(EntityPickupItemEvent event) {
+        this.cancelIfLocked(event.getEntity(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onLaunch(ProjectileLaunchEvent event) {
+        this.cancelIfLocked(event.getEntity().getShooter(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onGlide(EntityToggleGlideEvent event) {
+        if(event.isGliding()) this.cancelIfLocked(event.getEntity(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onHunger(FoodLevelChangeEvent event) {
+        this.cancelIfLocked(event.getEntity(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW)
+    public void onDamage(EntityDamageEvent event) {
+        this.cancelIfLocked(event.getEntity(), event);
+    }
+
+    /**
+     * Ender chests would keep items between fights.
+     */
+    @EventHandler
+    public void onOpen(InventoryOpenEvent event) {
+        if(event.getInventory().getType() == InventoryType.ENDER_CHEST) event.setCancelled(true);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ModeMenu.java

@@ -0,0 +1,74 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode;
+import eu.mhsl.craftattack.spawn.core.util.inventory.ItemBuilder;
+import eu.mhsl.craftattack.spawn.core.util.inventory.PlaceholderItems;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.text.format.TextDecoration;
+import org.bukkit.Bukkit;
+import org.bukkit.Material;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryHolder;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.SkullMeta;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Chest menu in which the challenger picks the mode. Works for Bedrock players as well.
+ */
+final class ModeMenu implements InventoryHolder {
+    private static final int[] SLOTS = {11, 13, 15};
+    private static final FightMode[] MODES = {FightMode.OWN, FightMode.CHALLENGER, FightMode.OPPONENT};
+
+    private final Inventory inventory;
+
+    private ModeMenu(Player challenger, FightMode current) {
+        this.inventory = Bukkit.createInventory(this, 27, Component.text("Wähle den Kampfmodus"));
+        for(int i = 0; i < this.inventory.getSize(); i++) this.inventory.setItem(i, PlaceholderItems.grayStainedGlassPane);
+        for(int i = 0; i < MODES.length; i++) this.inventory.setItem(SLOTS[i], this.item(MODES[i], challenger, MODES[i] == current));
+    }
+
+    static void open(Player challenger, FightMode current) {
+        challenger.openInventory(new ModeMenu(challenger, current).getInventory());
+    }
+
+    static boolean isOpen(Player player) {
+        return player.getOpenInventory().getTopInventory().getHolder(false) instanceof ModeMenu;
+    }
+
+    @Nullable FightMode modeAt(int slot) {
+        for(int i = 0; i < SLOTS.length; i++) {
+            if(SLOTS[i] == slot) return MODES[i];
+        }
+        return null;
+    }
+
+    private ItemStack item(FightMode mode, Player challenger, boolean selected) {
+        ItemBuilder builder = switch(mode) {
+            case OWN -> ItemBuilder.of(Material.IRON_SWORD)
+                .lore("Ihr kämpft beide mit eurem eigenen Inventar.");
+            case CHALLENGER -> ItemBuilder.of(Material.PLAYER_HEAD)
+                .withMeta(meta -> ((SkullMeta) meta).setOwningPlayer(challenger))
+                .lore("Ihr kämpft beide mit deinem Inventar.");
+            case OPPONENT -> ItemBuilder.of(Material.CHEST)
+                .lore("Ihr kämpft beide mit dem Inventar von dem, der sich auf das andere Feld stellt.");
+        };
+        builder.displayName(Component.text(mode.displayName(), NamedTextColor.GOLD).decoration(TextDecoration.ITALIC, false));
+        if(selected) {
+            builder.glint().appendLore(Component.empty())
+                .appendLore(Component.text("Ausgewählt", NamedTextColor.GREEN).decoration(TextDecoration.ITALIC, false));
+        } else {
+            builder.appendLore(Component.empty())
+                .appendLore(Component.text("Klicken zum Auswählen", NamedTextColor.YELLOW).decoration(TextDecoration.ITALIC, false));
+        }
+        return builder.build();
+    }
+
+    @Override
+    public @NotNull Inventory getInventory() {
+        return this.inventory;
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/ModeMenuListener.java

@@ -0,0 +1,21 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode;
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.inventory.InventoryClickEvent;
+
+class ModeMenuListener extends ApplianceListener<Arena> {
+    @EventHandler
+    public void onClick(InventoryClickEvent event) {
+        if(!(event.getView().getTopInventory().getHolder(false) instanceof ModeMenu menu)) return;
+        event.setCancelled(true);
+        if(!(event.getWhoClicked() instanceof Player player)) return;
+        if(event.getRawSlot() >= event.getView().getTopInventory().getSize()) return;
+
+        FightMode mode = menu.modeAt(event.getRawSlot());
+        Lobby lobby = this.getAppliance().lobby();
+        if(mode != null && lobby != null) lobby.chooseMode(player, mode);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/PlayerConnectionListener.java

@@ -0,0 +1,22 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.player.PlayerJoinEvent;
+import org.bukkit.event.player.PlayerQuitEvent;
+
+class PlayerConnectionListener extends ApplianceListener<Arena> {
+    @EventHandler
+    public void onJoin(PlayerJoinEvent event) {
+        event.getPlayer().getEnderChest().clear();
+        this.getAppliance().toTribune(event.getPlayer());
+        event.getPlayer().sendMessage(Style.message(
+            "Willkommen in der Arena! Stell dich auf ein Startfeld, um jemanden herauszufordern. Zurück geht es beim Villager oder mit /craftattack."
+        ));
+    }
+
+    @EventHandler
+    public void onQuit(PlayerQuitEvent event) {
+        this.getAppliance().handleQuit(event.getPlayer());
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Style.java

@@ -0,0 +1,55 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.text.format.TextColor;
+import org.bukkit.Color;
+import org.bukkit.Location;
+import org.bukkit.Sound;
+import org.bukkit.entity.Player;
+
+import java.util.Locale;
+
+/**
+ * Colors, texts and sounds of the arena, so everything looks and sounds the same everywhere.
+ * Player facing texts use no dashes.
+ */
+final class Style {
+    static final Component PREFIX = Component.text("[Arena] ", NamedTextColor.GOLD);
+
+    static final NamedTextColor[] PAD_TEXT_COLORS = {NamedTextColor.RED, NamedTextColor.BLUE};
+    static final Color[] PAD_PARTICLE_COLORS = {Color.fromRGB(255, 70, 70), Color.fromRGB(80, 120, 255)};
+    static final String[] PAD_NAMES = {"Rotes Feld", "Blaues Feld"};
+    static final Color WAITING_PARTICLE_COLOR = Color.fromRGB(150, 150, 150);
+
+    private Style() {
+    }
+
+    static Component message(String text) {
+        return PREFIX.append(Component.text(text, NamedTextColor.GRAY));
+    }
+
+    static Component message(Component text) {
+        return PREFIX.append(text.colorIfAbsent(NamedTextColor.GRAY));
+    }
+
+    static Component name(String name, TextColor color) {
+        return Component.text(name, color);
+    }
+
+    static String hearts(double health) {
+        return String.format(Locale.GERMAN, "%.1f", health / 2);
+    }
+
+    static String time(int seconds) {
+        return String.format("%d:%02d", seconds / 60, seconds % 60);
+    }
+
+    static void play(Player player, Sound sound, float pitch) {
+        player.playSound(player, sound, 1f, pitch);
+    }
+
+    static void play(Location location, Sound sound, float volume, float pitch) {
+        location.getWorld().playSound(location, sound, volume, pitch);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/Teams.java

@@ -0,0 +1,48 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.scoreboard.Scoreboard;
+import org.bukkit.scoreboard.Team;
+
+/**
+ * Scoreboard teams for the colored names. Players on a pad cannot be pushed (no collision),
+ * on the tribune and in a fight collision stays on.
+ */
+final class Teams {
+    private static final String[] NAMES = {"arena_pad_red", "arena_pad_blue", "arena_fight_red", "arena_fight_blue"};
+
+    private final Team[] teams = new Team[NAMES.length];
+
+    Teams() {
+        Scoreboard scoreboard = Bukkit.getScoreboardManager().getMainScoreboard();
+        for(int i = 0; i < NAMES.length; i++) {
+            Team team = scoreboard.getTeam(NAMES[i]);
+            if(team == null) team = scoreboard.registerNewTeam(NAMES[i]);
+            team.color(Style.PAD_TEXT_COLORS[i % 2]);
+            team.setOption(Team.Option.COLLISION_RULE, i < 2 ? Team.OptionStatus.NEVER : Team.OptionStatus.ALWAYS);
+            this.teams[i] = team;
+        }
+    }
+
+    static int pad(int pad) {
+        return pad;
+    }
+
+    static int fight(int side) {
+        return 2 + side;
+    }
+
+    void join(Player player, int team) {
+        this.leave(player);
+        this.teams[team].addEntry(player.getName());
+    }
+
+    void leave(Player player) {
+        for(Team team : this.teams) team.removeEntry(player.getName());
+    }
+
+    void clear() {
+        for(Team team : this.teams) team.getEntries().forEach(team::removeEntry);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/WorldProtectionListener.java

@@ -0,0 +1,145 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena;
+
+import eu.mhsl.craftattack.spawn.core.appliance.ApplianceListener;
+import org.bukkit.Location;
+import org.bukkit.block.Block;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.block.BlockBreakEvent;
+import org.bukkit.event.block.BlockBurnEvent;
+import org.bukkit.event.block.BlockExplodeEvent;
+import org.bukkit.event.block.BlockFadeEvent;
+import org.bukkit.event.block.BlockFormEvent;
+import org.bukkit.event.block.BlockFromToEvent;
+import org.bukkit.event.block.BlockIgniteEvent;
+import org.bukkit.event.block.BlockPistonExtendEvent;
+import org.bukkit.event.block.BlockPistonRetractEvent;
+import org.bukkit.event.block.BlockPlaceEvent;
+import org.bukkit.event.block.BlockSpreadEvent;
+import org.bukkit.event.block.LeavesDecayEvent;
+import org.bukkit.event.entity.EntityChangeBlockEvent;
+import org.bukkit.event.entity.EntityExplodeEvent;
+import org.bukkit.event.hanging.HangingPlaceEvent;
+import org.bukkit.event.player.PlayerBucketEmptyEvent;
+import org.bukkit.event.player.PlayerBucketFillEvent;
+import org.bukkit.event.world.StructureGrowEvent;
+
+import java.util.List;
+
+/**
+ * In the play world blocks may only change inside the arenas. Everything else (tribune, pads, the space
+ * between arenas) stays exactly as in the template.
+ */
+class WorldProtectionListener extends ApplianceListener<Arena> {
+    private boolean isProtected(Block block) {
+        return this.isProtected(block.getLocation());
+    }
+
+    private boolean isProtected(Location location) {
+        if(!this.getAppliance().worlds().isPlay(location.getWorld())) return false;
+        return !this.getAppliance().isInsideArena(location);
+    }
+
+    private void cancelIfProtected(Block block, Cancellable event) {
+        if(this.isProtected(block)) event.setCancelled(true);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onPlace(BlockPlaceEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onBreak(BlockBreakEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onBucketEmpty(PlayerBucketEmptyEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onBucketFill(PlayerBucketFillEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onFlow(BlockFromToEvent event) {
+        this.cancelIfProtected(event.getToBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onSpread(BlockSpreadEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onForm(BlockFormEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onFade(BlockFadeEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onIgnite(BlockIgniteEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onBurn(BlockBurnEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onLeavesDecay(LeavesDecayEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onEntityChangeBlock(EntityChangeBlockEvent event) {
+        this.cancelIfProtected(event.getBlock(), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onHangingPlace(HangingPlaceEvent event) {
+        this.cancelIfProtected(event.getBlock().getRelative(event.getBlockFace()), event);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onGrow(StructureGrowEvent event) {
+        if(!this.getAppliance().worlds().isPlay(event.getWorld())) return;
+        event.getBlocks().removeIf(state -> this.isProtected(state.getLocation()));
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onPistonExtend(BlockPistonExtendEvent event) {
+        if(this.anyProtected(event.getBlock(), event.getBlocks(), event.getDirection().getModX(), event.getDirection().getModY(), event.getDirection().getModZ()))
+            event.setCancelled(true);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onPistonRetract(BlockPistonRetractEvent event) {
+        if(this.anyProtected(event.getBlock(), event.getBlocks(), event.getDirection().getModX(), event.getDirection().getModY(), event.getDirection().getModZ()))
+            event.setCancelled(true);
+    }
+
+    private boolean anyProtected(Block piston, List<Block> moved, int dx, int dy, int dz) {
+        if(this.isProtected(piston) || this.isProtected(piston.getRelative(dx, dy, dz))) return true;
+        return moved.stream().anyMatch(block -> this.isProtected(block) || this.isProtected(block.getRelative(dx, dy, dz)));
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onEntityExplode(EntityExplodeEvent event) {
+        event.blockList().removeIf(this::isProtected);
+    }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onBlockExplode(BlockExplodeEvent event) {
+        event.blockList().removeIf(this::isProtected);
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/FightMode.java

@@ -0,0 +1,36 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+/**
+ * Which inventory the two fighters use. The challenger chooses it.
+ */
+public enum FightMode {
+    OWN("Jeder sein eigenes"),
+    CHALLENGER("Beide mit meinem"),
+    OPPONENT("Beide mit dem des Gegners");
+
+    public enum Role {
+        CHALLENGER,
+        OPPONENT
+    }
+
+    private final String displayName;
+
+    FightMode(String displayName) {
+        this.displayName = displayName;
+    }
+
+    public String displayName() {
+        return this.displayName;
+    }
+
+    /**
+     * @return whose inventory the fighter with the given role gets
+     */
+    public Role kitSource(Role fighter) {
+        return switch(this) {
+            case OWN -> fighter;
+            case CHALLENGER -> Role.CHALLENGER;
+            case OPPONENT -> Role.OPPONENT;
+        };
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/PadLobby.java

@@ -0,0 +1,164 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+import org.jetbrains.annotations.Nullable;
+
+import java.util.UUID;
+
+/**
+ * State of the two start pads. The first player on a pad becomes the challenger and picks the mode,
+ * stepping on the other pad means accepting. Once both stand there long enough, the fight starts.
+ */
+public class PadLobby {
+    public static final int PADS = 2;
+
+    public interface Listener {
+        /** The player is now the challenger and should pick a mode. */
+        void challengerSelected(UUID challenger);
+
+        /** Both pads are taken: give both the inventories of the chosen mode. */
+        void kitsApplied(UUID challenger, UUID opponent, FightMode mode);
+
+        /** The player gets the own inventory back. */
+        void kitReverted(UUID player);
+
+        void countdown(int secondsLeft);
+
+        void countdownCancelled();
+
+        void start(UUID challenger, UUID opponent, FightMode mode, int challengerPad);
+    }
+
+    private final Listener listener;
+    private final int countdownTicks;
+    private final UUID[] occupants = new UUID[PADS];
+    private int challengerPad = -1;
+    private FightMode mode = FightMode.OWN;
+    private int ticksLeft = -1;
+
+    public PadLobby(Listener listener, int countdownSeconds) {
+        this.listener = listener;
+        this.countdownTicks = countdownSeconds * 20;
+    }
+
+    /**
+     * @return false if the pad is already taken
+     */
+    public boolean enter(int pad, UUID player) {
+        if(this.occupants[pad] != null) return false;
+        if(this.padOf(player) != -1) return false;
+
+        this.occupants[pad] = player;
+        if(this.challengerPad == -1) {
+            this.challengerPad = pad;
+            this.mode = FightMode.OWN;
+            this.listener.challengerSelected(player);
+            return true;
+        }
+
+        this.listener.kitsApplied(this.challenger(), this.opponent(), this.mode);
+        this.ticksLeft = this.countdownTicks;
+        return true;
+    }
+
+    public void leave(UUID player) {
+        int pad = this.padOf(player);
+        if(pad == -1) return;
+
+        int other = 1 - pad;
+        boolean bothThere = this.isFull();
+        this.occupants[pad] = null;
+        this.listener.kitReverted(player);
+        if(bothThere) {
+            this.ticksLeft = -1;
+            this.listener.kitReverted(this.occupants[other]);
+            this.listener.countdownCancelled();
+        }
+
+        if(pad != this.challengerPad) return;
+        if(this.occupants[other] == null) {
+            this.challengerPad = -1;
+            return;
+        }
+        this.challengerPad = other;
+        this.mode = FightMode.OWN;
+        this.listener.challengerSelected(this.occupants[other]);
+    }
+
+    /**
+     * Only the challenger can change the mode, and only while nobody stands on the other pad.
+     */
+    public boolean setMode(UUID player, FightMode mode) {
+        if(!player.equals(this.challenger()) || this.isFull()) return false;
+        this.mode = mode;
+        return true;
+    }
+
+    /**
+     * Called every server tick. The countdown only runs while an arena is free.
+     */
+    public void tick(boolean arenaAvailable) {
+        if(this.ticksLeft < 0) return;
+        if(!arenaAvailable) {
+            this.ticksLeft = this.countdownTicks;
+            return;
+        }
+
+        if(this.ticksLeft % 20 == 0 && this.ticksLeft > 0) this.listener.countdown(this.ticksLeft / 20);
+        if(this.ticksLeft-- > 0) return;
+
+        UUID challenger = this.challenger();
+        UUID opponent = this.opponent();
+        FightMode mode = this.mode;
+        int challengerPad = this.challengerPad;
+        this.occupants[0] = null;
+        this.occupants[1] = null;
+        this.challengerPad = -1;
+        this.mode = FightMode.OWN;
+        this.ticksLeft = -1;
+        this.listener.start(challenger, opponent, mode, challengerPad);
+    }
+
+    public int padOf(UUID player) {
+        for(int i = 0; i < PADS; i++) {
+            if(player.equals(this.occupants[i])) return i;
+        }
+        return -1;
+    }
+
+    public @Nullable UUID occupant(int pad) {
+        return this.occupants[pad];
+    }
+
+    public @Nullable UUID challenger() {
+        return this.challengerPad == -1 ? null : this.occupants[this.challengerPad];
+    }
+
+    public @Nullable UUID opponent() {
+        return this.challengerPad == -1 ? null : this.occupants[1 - this.challengerPad];
+    }
+
+    public int challengerPad() {
+        return this.challengerPad;
+    }
+
+    public FightMode mode() {
+        return this.mode;
+    }
+
+    public boolean isFull() {
+        return this.occupants[0] != null && this.occupants[1] != null;
+    }
+
+    public boolean isCountingDown() {
+        return this.ticksLeft >= 0;
+    }
+
+    public boolean isIdle() {
+        return this.occupants[0] == null && this.occupants[1] == null;
+    }
+
+    /** Seconds until the start, rounded up; -1 without countdown. */
+    public int secondsLeft() {
+        return this.ticksLeft < 0 ? -1 : (this.ticksLeft + 19) / 20;
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/Region.java

@@ -0,0 +1,58 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+/**
+ * Axis-aligned box of whole blocks, both corners inclusive.
+ */
+public record Region(int minX, int minY, int minZ, int maxX, int maxY, int maxZ) {
+    public static Region of(int x1, int y1, int z1, int x2, int y2, int z2) {
+        return new Region(
+            Math.min(x1, x2), Math.min(y1, y2), Math.min(z1, z2),
+            Math.max(x1, x2), Math.max(y1, y2), Math.max(z1, z2)
+        );
+    }
+
+    public boolean contains(int x, int y, int z) {
+        return x >= this.minX && x <= this.maxX
+            && y >= this.minY && y <= this.maxY
+            && z >= this.minZ && z <= this.maxZ;
+    }
+
+    public boolean contains(double x, double y, double z) {
+        return this.contains((int) Math.floor(x), (int) Math.floor(y), (int) Math.floor(z));
+    }
+
+    public Region expand(int horizontal, int up) {
+        return new Region(
+            this.minX - horizontal, this.minY, this.minZ - horizontal,
+            this.maxX + horizontal, this.maxY + up, this.maxZ + horizontal
+        );
+    }
+
+    public long volume() {
+        return (long) (this.maxX - this.minX + 1) * (this.maxY - this.minY + 1) * (this.maxZ - this.minZ + 1);
+    }
+
+    public double centerX() {
+        return (this.minX + this.maxX + 1) / 2.0;
+    }
+
+    public double centerZ() {
+        return (this.minZ + this.maxZ + 1) / 2.0;
+    }
+
+    public int minChunkX() {
+        return this.minX >> 4;
+    }
+
+    public int maxChunkX() {
+        return this.maxX >> 4;
+    }
+
+    public int minChunkZ() {
+        return this.minZ >> 4;
+    }
+
+    public int maxChunkZ() {
+        return this.maxZ >> 4;
+    }
+}

arena/src/main/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/ResetCursor.java

@@ -0,0 +1,52 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+/**
+ * Walks through every block of a region in portions, so a reset can be spread over several ticks.
+ */
+public class ResetCursor {
+    @FunctionalInterface
+    public interface BlockVisitor {
+        void visit(int x, int y, int z);
+    }
+
+    private final Region region;
+    private int x;
+    private int y;
+    private int z;
+    private boolean done;
+
+    public ResetCursor(Region region) {
+        this.region = region;
+        this.x = region.minX();
+        this.y = region.minY();
+        this.z = region.minZ();
+    }
+
+    /**
+     * Visits up to {@code budget} blocks, continuing where the last call stopped.
+     *
+     * @return number of visited blocks
+     */
+    public int advance(int budget, BlockVisitor visitor) {
+        int visited = 0;
+        while(!this.done && visited < budget) {
+            visitor.visit(this.x, this.y, this.z);
+            visited++;
+            this.step();
+        }
+        return visited;
+    }
+
+    public boolean isDone() {
+        return this.done;
+    }
+
+    private void step() {
+        if(++this.y <= this.region.maxY()) return;
+        this.y = this.region.minY();
+        if(++this.z <= this.region.maxZ()) return;
+        this.z = this.region.minZ();
+        if(++this.x <= this.region.maxX()) return;
+        this.done = true;
+    }
+}

arena/src/test/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/FightModeTest.java

@@ -0,0 +1,27 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+import org.junit.jupiter.api.Test;
+
+import static eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode.Role.CHALLENGER;
+import static eu.mhsl.craftattack.spawn.arena.appliances.arena.logic.FightMode.Role.OPPONENT;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class FightModeTest {
+    @Test
+    void ownKeepsEveryonesInventory() {
+        assertEquals(CHALLENGER, FightMode.OWN.kitSource(CHALLENGER));
+        assertEquals(OPPONENT, FightMode.OWN.kitSource(OPPONENT));
+    }
+
+    @Test
+    void challengerKitForBoth() {
+        assertEquals(CHALLENGER, FightMode.CHALLENGER.kitSource(CHALLENGER));
+        assertEquals(CHALLENGER, FightMode.CHALLENGER.kitSource(OPPONENT));
+    }
+
+    @Test
+    void opponentKitForBoth() {
+        assertEquals(OPPONENT, FightMode.OPPONENT.kitSource(CHALLENGER));
+        assertEquals(OPPONENT, FightMode.OPPONENT.kitSource(OPPONENT));
+    }
+}

arena/src/test/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/PadLobbyTest.java

@@ -0,0 +1,151 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PadLobbyTest {
+    private final UUID a = UUID.randomUUID();
+    private final UUID b = UUID.randomUUID();
+    private final UUID c = UUID.randomUUID();
+    private final List<String> events = new ArrayList<>();
+    private PadLobby lobby;
+
+    @BeforeEach
+    void setUp() {
+        this.lobby = new PadLobby(new PadLobby.Listener() {
+            public void challengerSelected(UUID challenger) {
+                PadLobbyTest.this.events.add("challenger " + PadLobbyTest.this.name(challenger));
+            }
+
+            public void kitsApplied(UUID challenger, UUID opponent, FightMode mode) {
+                PadLobbyTest.this.events.add("kits " + PadLobbyTest.this.name(challenger) + PadLobbyTest.this.name(opponent) + " " + mode);
+            }
+
+            public void kitReverted(UUID player) {
+                PadLobbyTest.this.events.add("revert " + PadLobbyTest.this.name(player));
+            }
+
+            public void countdown(int secondsLeft) {
+                PadLobbyTest.this.events.add("countdown " + secondsLeft);
+            }
+
+            public void countdownCancelled() {
+                PadLobbyTest.this.events.add("cancelled");
+            }
+
+            public void start(UUID challenger, UUID opponent, FightMode mode, int challengerPad) {
+                PadLobbyTest.this.events.add("start " + PadLobbyTest.this.name(challenger) + PadLobbyTest.this.name(opponent) + " " + mode + " " + challengerPad);
+            }
+        }, 2);
+    }
+
+    private String name(UUID uuid) {
+        if(uuid.equals(this.a)) return "a";
+        if(uuid.equals(this.b)) return "b";
+        return "c";
+    }
+
+    @Test
+    void firstOnPadBecomesChallenger() {
+        assertTrue(this.lobby.enter(1, this.a));
+        assertEquals(List.of("challenger a"), this.events);
+        assertEquals(this.a, this.lobby.challenger());
+        assertNull(this.lobby.opponent());
+        assertFalse(this.lobby.isCountingDown());
+    }
+
+    @Test
+    void takenPadIsRefused() {
+        this.lobby.enter(0, this.a);
+        assertFalse(this.lobby.enter(0, this.b));
+        assertFalse(this.lobby.enter(1, this.a), "a player can only take one pad");
+    }
+
+    @Test
+    void secondPlayerAppliesKitsAndStartsAfterCountdown() {
+        this.lobby.enter(0, this.a);
+        assertTrue(this.lobby.setMode(this.a, FightMode.CHALLENGER));
+        this.lobby.enter(1, this.b);
+        assertFalse(this.lobby.setMode(this.a, FightMode.OWN), "mode is fixed once the opponent stands there");
+
+        for(int i = 0; i < 41; i++) this.lobby.tick(true);
+
+        assertEquals(List.of(
+            "challenger a",
+            "kits ab CHALLENGER",
+            "countdown 2",
+            "countdown 1",
+            "start ab CHALLENGER 0"
+        ), this.events);
+        assertTrue(this.lobby.isIdle());
+        assertNull(this.lobby.challenger());
+    }
+
+    @Test
+    void onlyChallengerMayChangeMode() {
+        this.lobby.enter(0, this.a);
+        assertFalse(this.lobby.setMode(this.b, FightMode.OPPONENT));
+        assertEquals(FightMode.OWN, this.lobby.mode());
+    }
+
+    @Test
+    void countdownWaitsForFreeArena() {
+        this.lobby.enter(0, this.a);
+        this.lobby.enter(1, this.b);
+        for(int i = 0; i < 100; i++) this.lobby.tick(false);
+        assertFalse(this.events.contains("countdown 2"));
+        assertEquals(2, this.lobby.secondsLeft());
+
+        for(int i = 0; i < 41; i++) this.lobby.tick(true);
+        assertTrue(this.events.contains("start ab OWN 0"));
+    }
+
+    @Test
+    void opponentLeavingCancelsAndRevertsBoth() {
+        this.lobby.enter(0, this.a);
+        this.lobby.setMode(this.a, FightMode.OPPONENT);
+        this.lobby.enter(1, this.b);
+        this.events.clear();
+
+        this.lobby.leave(this.b);
+
+        assertEquals(List.of("revert b", "revert a", "cancelled"), this.events);
+        assertEquals(this.a, this.lobby.challenger());
+        assertEquals(FightMode.OPPONENT, this.lobby.mode(), "challenger keeps the chosen mode");
+        assertFalse(this.lobby.isCountingDown());
+    }
+
+    @Test
+    void challengerLeavingHandsOverRole() {
+        this.lobby.enter(0, this.a);
+        this.lobby.setMode(this.a, FightMode.CHALLENGER);
+        this.lobby.enter(1, this.b);
+        this.events.clear();
+
+        this.lobby.leave(this.a);
+
+        assertEquals(List.of("revert a", "revert b", "cancelled", "challenger b"), this.events);
+        assertEquals(this.b, this.lobby.challenger());
+        assertEquals(1, this.lobby.challengerPad());
+        assertEquals(FightMode.OWN, this.lobby.mode());
+
+        this.lobby.enter(0, this.c);
+        assertEquals("kits bc OWN", this.events.getLast());
+    }
+
+    @Test
+    void lastPlayerLeavingResetsLobby() {
+        this.lobby.enter(0, this.a);
+        this.lobby.leave(this.a);
+        assertTrue(this.lobby.isIdle());
+        assertNull(this.lobby.challenger());
+        this.lobby.leave(this.b);
+        assertEquals(List.of("challenger a", "revert a"), this.events);
+    }
+}

arena/src/test/java/eu/mhsl/craftattack/spawn/arena/appliances/arena/logic/RegionTest.java

@@ -0,0 +1,52 @@
+package eu.mhsl.craftattack.spawn.arena.appliances.arena.logic;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class RegionTest {
+    @Test
+    void cornersAreNormalized() {
+        assertEquals(new Region(-2, 1, -5, 3, 4, 6), Region.of(3, 4, -5, -2, 1, 6));
+    }
+
+    @Test
+    void containsIsInclusiveAndFloorsNegativeCoordinates() {
+        Region region = Region.of(-2, 0, -2, 1, 3, 1);
+        assertTrue(region.contains(-2, 0, -2));
+        assertTrue(region.contains(1, 3, 1));
+        assertFalse(region.contains(2, 0, 0));
+        assertTrue(region.contains(-1.5, 0.0, 1.99));
+        assertFalse(region.contains(-2.01, 0.0, 0.0));
+        assertFalse(region.contains(1.0, 4.0, 0.0));
+    }
+
+    @Test
+    void volumeAndChunks() {
+        Region region = Region.of(-1, 0, 15, 16, 9, 32);
+        assertEquals(18L * 10 * 18, region.volume());
+        assertEquals(-1, region.minChunkX());
+        assertEquals(1, region.maxChunkX());
+        assertEquals(0, region.minChunkZ());
+        assertEquals(2, region.maxChunkZ());
+    }
+
+    @Test
+    void resetCursorVisitsEveryBlockOnceInPortions() {
+        Region region = Region.of(0, 0, 0, 4, 3, 2);
+        ResetCursor cursor = new ResetCursor(region);
+        Set<String> visited = new HashSet<>();
+        int calls = 0;
+        while(!cursor.isDone()) {
+            int count = cursor.advance(7, (x, y, z) -> assertTrue(visited.add(x + "," + y + "," + z)));
+            assertTrue(count <= 7);
+            calls++;
+        }
+        assertEquals(region.volume(), visited.size());
+        assertEquals((int) Math.ceil(region.volume() / 7.0), calls);
+        assertEquals(0, cursor.advance(7, (x, y, z) -> fail()));
+    }
+}