Update layers for GameObjects and add EnemyDeathBehavior class

Assets/Scripts/Systems/EnemyDeathBehavior.cs

@@ -0,0 +1,15 @@
+using Interfaces;
+using UnityEngine;
+
+namespace Systems
+{
+    public class EnemyDeathBehavior : MonoBehaviour, IDeathBehavior
+    {
+        public void Die()
+        {
+            Destroy(gameObject);
+            // later let's add particle effects, sound effects, etc.
+            // and give player experience points
+        }
+    }
+}