added slowness to tetris

src/main/java/eu/mhsl/minenet/minigames/instance/game/stateless/types/tetris/Tetris.java

@@ -16,6 +16,8 @@ import net.minestom.server.event.player.PlayerTickEvent;
 import net.minestom.server.event.player.PlayerUseItemEvent;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
+import net.minestom.server.potion.Potion;
+import net.minestom.server.potion.PotionEffect;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Map;
@@ -71,6 +73,7 @@ class Tetris extends StatelessGame {
     @Override
     protected void onPlayerLeave(Player p) {
         this.tetrisGames.get(p).sidebar.removeViewer(p);
+        p.clearEffects();
         this.letPlayerLoose(p);
     }
 
@@ -156,6 +159,7 @@ class Tetris extends StatelessGame {
 
         p.teleport(tetrisGame.getPlayerSpawnPosition());
         tetrisGame.sidebar.addViewer(p);
+        p.addEffect(new Potion(PotionEffect.SLOWNESS, 4, Potion.INFINITE_DURATION));
 
         return super.onPlayerJoin(p);
     }