diff --git a/.gitignore b/.gitignore
index 1af6953..8fffb5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,3 +17,4 @@ osu!/
 .env
 .env.gitea
 
+*.uid
\ No newline at end of file
diff --git a/src/core/autoload/GameState.gd b/src/core/autoload/GameState.gd
index 0266330..af81b4d 100644
--- a/src/core/autoload/GameState.gd
+++ b/src/core/autoload/GameState.gd
@@ -1,5 +1,14 @@
 # GameState.gd
 extends Node
+# --- COLLISION LAYERS (TASK 4) ---
+const LAYER_ENVIRONMENT = 1  # Environment/terrain
+const LAYER_PLAYER = 2        # Player character
+const LAYER_ENEMY = 3         # Enemy mobs
+const LAYER_GOOSE_PROJECTILE = 4 # Goose projectiles
+const LAYER_TURRET = 5        # Fixed towers/turrets
+const LAYER_PICKUP = 6        # Currency, power-ups
+const LAYER_UI_TRIGGER = 7    # UI interaction zones
+
 var score = 0
 var currency = 100
 var current_wave = 0