developer mode mod: game's developer switch on (warp with a+s, river log cheat), keys for the hidden aux inputs (fly, heart and fruit, idols, coins) on both exe versions

src/main/java/com/eliasmueller/llamamod/exe/Site.java

@@ -204,6 +204,23 @@ public enum Site {
             0x6D9408,
             "render camera target x, y, z"),
     SINE(operand("8B 1C 8D ?? ?? ?? ?? 8B C8 0F AF CA", 3), 0x574318, 0x574318, "s32[4096] sine table, 4096 = 1.0"),
+    // developer mode
+    PROP_GET(
+            code("8B 44 24 0C 83 EC 10 3D 09 01 00 00 0F 87 ?? ?? ?? ?? FF 24 85 ?? ?? ?? ??"),
+            0x550E60,
+            0x550B80,
+            "strat property getter: switch over ids 0..0x109, jump table address (in .text) at +21"),
+    PAD_POLL_END(
+            code("A1 ?? ?? ?? ?? 5B 83 F8 01 76 0A C7 05 ?? ?? ?? ?? 00 00 00 00 83 C4 08 C3"),
+            0x425B88,
+            0x425A08,
+            "end of PAD_BITS: clears PAD_AUX if more than one pad, then returns"),
+    PAD_AUX(operandAt(PAD_POLL_END, 13), 0x5FCF58, 0x5FC5E8, "aux pad bits (strat property 88), never set on PC"),
+    KEY_STATE(
+            operand("B9 00 01 00 00 33 C0 BF ?? ?? ?? ?? F3 AB B9 0F 00 00 00", 8),
+            0x58226C,
+            0x5818FC,
+            "s32[256] DirectInput keyboard state by DIK code (frames held, 0 = up)"),
     // base patch: level record relocation
     COINS(
             operand("8B 34 B5 ?? ?? ?? ?? C1 EE 0C 3B F2", 3),

src/main/java/com/eliasmueller/llamamod/mods/ModRegistry.java

@@ -25,6 +25,7 @@ public final class ModRegistry {
         "com.eliasmueller.llamamod.mods.freecam.FreeCamMod",
         "com.eliasmueller.llamamod.mods.arena.ArenaMod",
         "com.eliasmueller.llamamod.mods.coaster.CoasterMod",
+        "com.eliasmueller.llamamod.mods.devmode.DevModeMod",
     };
 
     /** {@link ModSource}s loaded by class name (dynamic mods, e.g. level projects). */

src/main/java/com/eliasmueller/llamamod/mods/devmode/DevModeMod.java

@@ -0,0 +1,92 @@
+package com.eliasmueller.llamamod.mods.devmode;
+
+import com.eliasmueller.llamamod.mods.Hotkeys;
+import com.eliasmueller.llamamod.mods.Mod;
+import com.eliasmueller.llamamod.mods.ModContext;
+import com.eliasmueller.llamamod.mods.ModOption;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/** The game's hidden developer switch and its PC-less aux pad buttons (see {@link DevModePatch}). */
+public final class DevModeMod implements Mod {
+    record AuxKey(String option, String label, String description, String def, int bit) {}
+
+    static final List<AuxKey> KEYS = List.of(
+            new AuxKey(
+                    "flyKey",
+                    "Fly key",
+                    "Hold to fly: the llama (also from standing), the bunny and the frog (after a jump) rise"
+                            + " while the key is held.",
+                    "F1",
+                    DevModePatch.AUX_FLY),
+            new AuxKey(
+                    "heartKey",
+                    "Heart and fruit key",
+                    "Each press gives one heart and 5 purple fruit.",
+                    "F2",
+                    DevModePatch.AUX_HEART),
+            new AuxKey("idolKey", "Idol key", "Hold to count the pink idols up (to 99).", "F3", DevModePatch.AUX_IDOLS),
+            new AuxKey("coinKey", "Coin key", "Hold to count the coins up fast.", "F11", DevModePatch.AUX_COINS));
+
+    @Override
+    public String id() {
+        return "devmode";
+    }
+
+    @Override
+    public String name() {
+        return "Developer mode";
+    }
+
+    @Override
+    public String category() {
+        return CHEATS;
+    }
+
+    @Override
+    public String description() {
+        return "Turns on the game's hidden developer switch and puts its extra buttons on the keyboard."
+                + " Hold A+S to warp the llama to the developers' warp points (22 levels, they go round in a"
+                + " circle). Hold F1 to fly, press F2 for a heart and 5 fruit, hold F3 for idols and F11 for"
+                + " coins (keys can be changed below). On the river log (world 3) hold Space: no damage, through"
+                + " the banks, very fast. In the finale, holding Space+Z ends the level. The developers'"
+                + " level-skip and music menu stays unavailable (it needs a second switch that is always off).";
+    }
+
+    @Override
+    public boolean modifiesExecutable() {
+        return true;
+    }
+
+    @Override
+    public List<ModOption> options() {
+        List<ModOption> o = new ArrayList<>();
+        for (AuxKey k : KEYS) {
+            o.add(Hotkeys.option(k.option(), k.label(), k.description(), k.def()));
+        }
+        o.add(ModOption.bool(
+                "flyToggle",
+                "Fly key switches on and off",
+                "Press the fly key once to start flying and again to stop, instead of holding it.",
+                false));
+        return o;
+    }
+
+    @Override
+    public void apply(ModContext ctx) throws IOException {
+        List<DevModePatch.Key> keys = new ArrayList<>();
+        Set<String> used = new HashSet<>();
+        for (AuxKey k : KEYS) {
+            String v = ctx.option(k.option());
+            if (!used.add(v)) {
+                throw new IllegalArgumentException("Developer mode: " + v + " is used for two keys");
+            }
+            keys.add(new DevModePatch.Key(DevModePatch.dik(v), k.bit()));
+        }
+        DevModePatch.enableDeveloperFlag(ctx.exe());
+        DevModePatch.mapAuxKeys(ctx.exe(), keys, ctx.optionBool("flyToggle"));
+    }
+}

src/main/java/com/eliasmueller/llamamod/mods/devmode/DevModePatch.java

@@ -0,0 +1,162 @@
+package com.eliasmueller.llamamod.mods.devmode;
+
+import static com.eliasmueller.llamamod.mods.practice.Asm.EAX;
+import static com.eliasmueller.llamamod.mods.practice.Asm.EBX;
+import static com.eliasmueller.llamamod.mods.practice.Asm.ECX;
+
+import com.eliasmueller.llamamod.exe.ExeImage;
+import com.eliasmueller.llamamod.exe.ExePatchException;
+import com.eliasmueller.llamamod.exe.GameExe;
+import com.eliasmueller.llamamod.exe.Site;
+import com.eliasmueller.llamamod.exe.X86;
+import com.eliasmueller.llamamod.mods.practice.Asm;
+import java.util.HexFormat;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Developer switch and aux pad keys (German exe addresses; the code uses the {@link Site}s).
+ *
+ * <ul>
+ *   <li>Strat property 258 (0x102) is a developer flag the getter FUN_00550e60 hard-wires to 0:
+ *       jump table 0x552684[0x102] (= 0x552A8C) → shared handler 0x55231B {@code push 0} (also
+ *       ids 0x75, 0x9E, 0xC1, 0xEE). The table entry is pointed at a cave that pushes 0x1000 (1.0
+ *       in 20.12); the shared handler stays untouched.
+ *   <li>padAux (property 88, 0x5FCF58) is never set on PC. The tail of the pad poll FUN_004256c0
+ *       (0x425B88: {@code if (padCount > 1) padAux = 0; return}) is replaced by a cave that builds
+ *       padAux from the DirectInput key state 0x58226C[DIK] (0 while a demo plays). The edge
+ *       detection padAuxPressed (0x5FCF60, FUN_00425c00 at the start of every tick) runs after
+ *       it as before.
+ * </ul>
+ */
+public final class DevModePatch {
+    /** Developer flag property id and the value the cave pushes. */
+    static final int PROP_DEV = 0x102, ONE = 0x1000;
+
+    /** padAux bits read by the strats. */
+    static final int AUX_COINS = 0x100, AUX_IDOLS = 0x200, AUX_HEART = 0x400, AUX_FLY = 0x800;
+
+    /** Original shared handler of property 258: {@code mov eax,[esp+14h]; push 0; push eax; call push; ...; ret}. */
+    static final String ZERO_HANDLER = "8B 44 24 14 6A 00 50 E8 ?? ?? ?? ?? 83 C4 08 83 C4 10 C3";
+
+    /** DirectInput scan codes of the {@link com.eliasmueller.llamamod.mods.Hotkeys} choices. */
+    static final Map<String, Integer> DIK = Map.ofEntries(
+            Map.entry("F1", 0x3B),
+            Map.entry("F2", 0x3C),
+            Map.entry("F3", 0x3D),
+            Map.entry("F4", 0x3E),
+            Map.entry("F5", 0x3F),
+            Map.entry("F7", 0x41),
+            Map.entry("F8", 0x42),
+            Map.entry("F9", 0x43),
+            Map.entry("F11", 0x57),
+            Map.entry("F12", 0x58),
+            Map.entry("Insert", 0xD2),
+            Map.entry("Delete", 0xD3),
+            Map.entry("Home", 0xC7),
+            Map.entry("End", 0xCF));
+
+    /** A key that sets padAux {@code bit} while held. */
+    record Key(int dik, int bit) {}
+
+    private DevModePatch() {}
+
+    static int dik(String hotkey) {
+        Integer v = DIK.get(hotkey);
+        if (v == null) {
+            throw new IllegalArgumentException("unknown hotkey " + hotkey);
+        }
+        return v;
+    }
+
+    /** Sets property 258 to 1.0. */
+    public static void enableDeveloperFlag(ExeImage exe) throws ExePatchException {
+        GameExe g = exe.game();
+        long table = exe.readU32(g.va(Site.PROP_GET) + 21);
+        long entry = table + 4L * PROP_DEV;
+        long handler = exe.readU32(entry);
+        String got = hex(exe.readOriginal(handler, 19));
+        if (!matches(got, ZERO_HANDLER)) {
+            throw new ExePatchException("devmode: property 258 handler at " + ExeImage.hexVa(handler) + " is " + got
+                    + ", expected " + ZERO_HANDLER + " – unknown program version");
+        }
+        long push = handler + 12 + (int) exe.readU32(handler + 8);
+        long fn = exe.emit("devmode: property 258 = 1", a -> {
+            a.hex("8B 44 24 14"); // mov eax,[esp+14h]
+            a.push(ONE);
+            a.u8(0x50); // push eax
+            a.call(push);
+            a.hex("83 C4 08 83 C4 10"); // add esp,8; add esp,10h
+            a.ret();
+        });
+        exe.patch(entry, le(handler), le(fn), "devmode: property 258 jump table entry");
+    }
+
+    /**
+     * padAux = OR of the bits whose key is held; {@code toggleFly}: the {@link #AUX_FLY} key (if in
+     * {@code keys}) switches the bit on and off instead.
+     */
+    public static void mapAuxKeys(ExeImage exe, List<Key> keys, boolean toggleFly) throws ExePatchException {
+        GameExe g = exe.game();
+        long tail = g.va(Site.PAD_POLL_END), aux = g.va(Site.PAD_AUX), state = g.va(Site.KEY_STATE);
+        long demo = g.va(Site.DEMO), padCount = g.va(Site.PAD_COUNT);
+        long d = toggleFly ? exe.allocateData(8, "devmode: fly toggle") : 0;
+        long prev = d, flyOn = d + 4;
+        long fn = exe.emit("devmode: aux pad keys", a -> {
+            Asm m = new Asm(a);
+            X86.Label store = a.label();
+            m.pop(EBX); // the original tail's pop ebx
+            m.push(ECX);
+            a.hex("33 C9"); // xor ecx,ecx
+            m.cmpMemImm(demo, 0);
+            a.jcc(X86.JNE, store);
+            for (Key k : keys) {
+                X86.Label skip = a.label();
+                long slot = state + 4L * k.dik();
+                if (toggleFly && k.bit() == AUX_FLY) {
+                    X86.Label same = a.label();
+                    a.hex("33 C0"); // xor eax,eax
+                    m.cmpMemImm(slot, 0);
+                    a.hex("0F 9F C0"); // setg al
+                    m.cmpMem(EAX, prev);
+                    m.store(prev, EAX);
+                    a.jcc(X86.JBE, same);
+                    m.xorMemImm(flyOn, 1);
+                    a.bind(same);
+                    m.cmpMemImm(flyOn, 0);
+                    a.jcc(X86.JE, skip);
+                } else {
+                    m.cmpMemImm(slot, 0);
+                    a.jcc(X86.JLE, skip);
+                }
+                a.hex("81 C9").u32(k.bit()); // or ecx,bit
+                a.bind(skip);
+            }
+            a.bind(store);
+            m.store(aux, ECX);
+            m.pop(ECX);
+            m.load(EAX, padCount);
+            a.hex("83 C4 08"); // add esp,8
+            a.ret();
+        });
+        exe.hookJmp(tail, g.original(Site.PAD_POLL_END, 25), fn, "devmode: pad poll tail");
+    }
+
+    private static boolean matches(String got, String pattern) {
+        String[] g = got.split(" "), p = pattern.split(" ");
+        for (int i = 0; i < p.length; i++) {
+            if (!p[i].equals("??") && !p[i].equals(g[i])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private static String hex(byte[] b) {
+        return HexFormat.ofDelimiter(" ").withUpperCase().formatHex(b);
+    }
+
+    private static byte[] le(long v) {
+        return new byte[] {(byte) v, (byte) (v >> 8), (byte) (v >> 16), (byte) (v >> 24)};
+    }
+}

src/test/java/com/eliasmueller/llamamod/exe/GameExeTest.java

@@ -50,7 +50,9 @@ class GameExeTest {
             Map.entry(Site.REGIONS_CALL_FRAME, "call 0x{REGIONS}"),
             Map.entry(Site.REGIONS_CALL_RUNNING, "call 0x{REGIONS}"),
             Map.entry(Site.REGIONS_CALL_PAUSED, "call 0x{REGIONS}"),
-            Map.entry(Site.STRAT_RESET, "mov DWORD PTR ds:0x"));
+            Map.entry(Site.STRAT_RESET, "mov DWORD PTR ds:0x"),
+            Map.entry(Site.PROP_GET, "mov eax,DWORD PTR [esp+0xc]"),
+            Map.entry(Site.PAD_POLL_END, "mov eax,ds:0x{PAD_COUNT}"));
 
     static byte[] bytes(String version) throws IOException {
         return Files.readAllBytes(GameData.exePath(version));

src/test/java/com/eliasmueller/llamamod/mods/ExeModCombinationsTest.java

@@ -23,7 +23,7 @@ import org.junit.jupiter.params.provider.ValueSource;
 
 /**
  * Every combination of the groove.exe mods (intro skip, cheats, practice, free camera, boot to
- * level), with default options and with every exe-relevant option switched on, must apply, give
+ * level, developer mode), with default options and with every exe-relevant option switched on, must apply, give
  * an executable that re-parses with a consistent section layout, replay byte-identically from the
  * cache and restore to the base exe (needs -Dllamamod.cd), for the German and the English exe.
  */
@@ -31,14 +31,15 @@ class ExeModCombinationsTest {
     @TempDir
     Path tmp;
 
-    private static final String[] IDS = {"intro-skip", "cheats", "practice", "freecam", "boot-to-level"};
+    private static final String[] IDS = {"intro-skip", "cheats", "practice", "freecam", "boot-to-level", "devmode"};
 
     /** Options that switch on every exe change of a mod (data-only options stay at their defaults). */
     private static final Map<String, Map<String, String>> ALL_ON = Map.of(
             "intro-skip", Map.of("logos", "true", "demo", "true", "story", "true"),
             "cheats", Map.of("diagnostics", "true"),
             "practice", Map.of("checkpoints", "false"),
-            "boot-to-level", Map.of("logos", "true", "quitOnEscape", "true"));
+            "boot-to-level", Map.of("logos", "true", "quitOnEscape", "true"),
+            "devmode", Map.of("flyToggle", "true"));
 
     /** {@code version}: "de" or "en" (the English exe runs against the German CD data here). */
     private AppPaths install(String version) throws IOException {

src/test/java/com/eliasmueller/llamamod/mods/ExeVersionsTest.java

@@ -39,7 +39,8 @@ class ExeVersionsTest {
                             "diagnostics", "true"),
             "practice", Map.of("checkpoints", "false"),
             "freecam", Map.of("freeze", "true"),
-            "boot-to-level", Map.of("logos", "true", "quitOnEscape", "true", "world", "3", "chapter", "2"));
+            "boot-to-level", Map.of("logos", "true", "quitOnEscape", "true", "world", "3", "chapter", "2"),
+            "devmode", Map.of("flyToggle", "true", "coinKey", "End"));
 
     /** SHA-256 of the German output before the version layer (2026-11-07); must never change. */
     static final Map<String, String> GERMAN_GOLDEN = Map.ofEntries(
@@ -56,7 +57,11 @@ class ExeVersionsTest {
             Map.entry("boot-to-level all", "e5663a945871409e4f0b3a701bcd82372daa4ca9846c00104309d30615d9b0ca"),
             Map.entry("freecam no freeze", "d93106a1b764a77e2e2ed7c01b9fc24e1b1f06112570074d04e6b005d806bd31"),
             Map.entry("all mods defaults", "9c18d4f6ea86b5e9e42eba092d3b1020d80a61c735c0a827b0dbf5baf407d942"),
-            Map.entry("all mods all", "dc0637ea12677d6595a06332e42ac319cae99f9267918ee58fb2ea1d13209691"));
+            Map.entry("all mods all", "dc0637ea12677d6595a06332e42ac319cae99f9267918ee58fb2ea1d13209691"),
+            // added later (developer mode, 2026-11-08)
+            Map.entry("devmode defaults", "0cbd6ef8cbeeb69d9187d50d1c292d7c31d1b0ebf79376b1ddc67e27b1e66d60"),
+            Map.entry("devmode all", "919fed192f1120301487292a38b2f7cd60480166140193f865f49b0ec7c94c1a"),
+            Map.entry("all mods and devmode all", "5c9a6d4e2687fe31fe944635c088287d979a0edf5b18abdcd7d0d5b4c3bb43dd"));
 
     static final List<String> IDS = List.of("intro-skip", "cheats", "practice", "freecam", "boot-to-level");
 
@@ -70,6 +75,11 @@ class ExeVersionsTest {
         l.add(new Config("freecam no freeze", List.of("freecam"), Map.of("freecam", Map.of("freeze", "false"))));
         l.add(new Config("all mods defaults", IDS, Map.of("practice", Map.of("checkpoints", "false"))));
         l.add(new Config("all mods all", IDS, ALL_ON));
+        l.add(new Config("devmode defaults", List.of("devmode"), Map.of()));
+        l.add(new Config("devmode all", List.of("devmode"), ALL_ON));
+        List<String> withDev = new java.util.ArrayList<>(IDS);
+        withDev.add("devmode");
+        l.add(new Config("all mods and devmode all", withDev, ALL_ON));
         return l;
     }
 

src/test/java/com/eliasmueller/llamamod/mods/devmode/DevModeModTest.java

@@ -0,0 +1,158 @@
+package com.eliasmueller.llamamod.mods.devmode;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.eliasmueller.llamamod.exe.ExeImage;
+import com.eliasmueller.llamamod.exe.GameExe;
+import com.eliasmueller.llamamod.exe.Site;
+import com.eliasmueller.llamamod.mods.GameData;
+import com.eliasmueller.llamamod.mods.Hotkeys;
+import com.eliasmueller.llamamod.mods.Mod;
+import com.eliasmueller.llamamod.mods.ModRegistry;
+import com.eliasmueller.llamamod.mods.TestModContext;
+import com.eliasmueller.llamamod.platform.Config;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HexFormat;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class DevModeModTest {
+    @TempDir
+    Path tmp;
+
+    private static ExeImage exe(String version) throws Exception {
+        return ExeImage.parse(Files.readAllBytes(GameData.exePath(version)));
+    }
+
+    private static ExeImage applied(String version, Map<String, String> opts, Path tmp) throws Exception {
+        ExeImage img = exe(version);
+        img.setOwner("devmode");
+        DevModeMod mod = new DevModeMod();
+        mod.apply(new TestModContext(tmp, mod, opts, img));
+        return img;
+    }
+
+    private static long rel(ExeImage img, long callAt) {
+        return callAt + 5 + (int) img.readU32(callAt + 1);
+    }
+
+    /** The aux key cave's code. */
+    private static String auxCave(ExeImage img) throws Exception {
+        ExeImage.Allocation a = img.journal("devmode").stream()
+                .filter(o -> o instanceof ExeImage.Allocation x && x.label().equals("devmode: aux pad keys"))
+                .map(o -> (ExeImage.Allocation) o)
+                .findFirst()
+                .orElseThrow();
+        assertEquals(rel(img, img.game().va(Site.PAD_POLL_END)), a.va());
+        return hex(img.read(a.va(), a.size()));
+    }
+
+    private static String hex(byte[] b) {
+        return HexFormat.ofDelimiter(" ").withUpperCase().formatHex(b);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"de", "en"})
+    void property258PushesOneAndTheSharedHandlerStays(String version) throws Exception {
+        ExeImage orig = exe(version);
+        ExeImage img = applied(version, Map.of(), tmp);
+        GameExe g = img.game();
+        long table = img.readU32(g.va(Site.PROP_GET) + 21);
+        long handler = orig.readU32(table + 4L * 0x102);
+        assertEquals(version.equals("de") ? 0x55231BL : 0x55198FL, handler);
+        long cave = img.readU32(table + 4L * 0x102);
+        assertTrue(cave >= img.caveStart(), ExeImage.hexVa(cave));
+        assertEquals("8B 44 24 14 68 00 10 00 00 50 E8", hex(img.read(cave, 11)));
+        assertEquals(rel(orig, handler + 7), rel(img, cave + 10));
+        assertEquals("83 C4 08 83 C4 10 C3", hex(img.read(cave + 15, 7)));
+        // every other table entry (the shared handler's other ids among them) is unchanged
+        for (int id = 0; id < 0x10A; id++) {
+            if (id != 0x102) {
+                assertEquals(orig.readU32(table + 4L * id), img.readU32(table + 4L * id), "id " + id);
+            }
+        }
+        assertArrayEquals(orig.read(handler, 19), img.read(handler, 19));
+        ExeImage.parse(img.build());
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"de", "en"})
+    void padPollTailBuildsPadAuxFromTheKeyState(String version) throws Exception {
+        ExeImage img = applied(version, Map.of(), tmp);
+        GameExe g = img.game();
+        long tail = g.va(Site.PAD_POLL_END);
+        assertEquals(0xE9, img.readU8(tail));
+        for (int i = 5; i < 25; i++) {
+            assertEquals(0x90, img.readU8(tail + i));
+        }
+        String h = auxCave(img);
+        assertTrue(h.startsWith("5B 51 33 C9 81 3D"), h); // pop ebx; push ecx; xor ecx,ecx; cmp [demo],0
+        long keys = g.va(Site.KEY_STATE);
+        int[][] expect = {{0x3B, 0x800}, {0x3C, 0x400}, {0x3D, 0x200}, {0x57, 0x100}};
+        int at = 0;
+        for (int[] e : expect) {
+            // cmp dword [keys + 4*dik], 0; jle; or ecx, bit
+            String want = "81 3D " + hex(le(keys + 4L * e[0])) + " 00 00 00 00 0F 8E";
+            at = h.indexOf(want, at);
+            assertTrue(at > 0, "key " + Integer.toHexString(e[0]));
+            assertTrue(h.indexOf("81 C9 " + hex(le(e[1])), at) > at);
+        }
+        String end =
+                "89 0D " + hex(le(g.va(Site.PAD_AUX))) + " 59 8B 05 " + hex(le(g.va(Site.PAD_COUNT))) + " 83 C4 08 C3";
+        assertTrue(h.contains(end), h);
+        ExeImage.parse(img.build());
+    }
+
+    @Test
+    void customKeysAndFlyToggle() throws Exception {
+        ExeImage img = applied("de", Map.of("flyKey", "Home", "coinKey", "F12", "flyToggle", "true"), tmp);
+        String h = auxCave(img);
+        long keys = img.game().va(Site.KEY_STATE);
+        assertTrue(h.contains("33 C0 81 3D " + hex(le(keys + 4L * 0xC7)) + " 00 00 00 00 0F 9F C0"), h);
+        assertTrue(h.contains("81 3D " + hex(le(keys + 4L * 0x58))), h);
+        assertTrue(img.journal("devmode").stream()
+                .anyMatch(o -> o instanceof ExeImage.Allocation a && a.label().equals("devmode: fly toggle")));
+    }
+
+    @Test
+    void sameKeyTwiceIsRejected() {
+        assertThrows(IllegalArgumentException.class, () -> applied("de", Map.of("idolKey", "F1"), tmp));
+    }
+
+    @Test
+    void everyHotkeyHasAScanCode() {
+        assertEquals(Hotkeys.VK.keySet(), DevModePatch.DIK.keySet());
+    }
+
+    @Test
+    void defaultKeysDoNotClashWithTheOtherHotkeyMods() {
+        ModRegistry reg = new ModRegistry();
+        List<Mod> mods = List.of(reg.get("practice"), reg.get("freecam"), reg.get("devmode"));
+        assertTrue(
+                Hotkeys.conflicts(mods, new Config()).isEmpty(),
+                Hotkeys.conflicts(mods, new Config()).toString());
+        for (DevModeMod.AuxKey k : DevModeMod.KEYS) {
+            assertTrue(!List.of("F4", "F6", "F7", "F10").contains(k.def()), k.def());
+        }
+    }
+
+    @Test
+    void registeredAsCheat() {
+        Mod m = new ModRegistry().get("devmode");
+        assertEquals(Mod.CHEATS, m.category());
+        assertTrue(m.modifiesExecutable());
+        assertTrue(m.description().contains("A+S") && m.description().contains("level-skip"));
+    }
+
+    private static byte[] le(long v) {
+        return new byte[] {(byte) v, (byte) (v >> 8), (byte) (v >> 16), (byte) (v >> 24)};
+    }
+}