Add attribute system with core stats and gameplay components

GameCore/Combat/DamageSystem.cs

@@ -0,0 +1,38 @@
+using GameCore.Attributes;
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+using GameCore.Events;
+using Attribute = GameCore.Attributes.Attribute;
+
+namespace GameCore.Combat;
+
+public class DamageSystem : ISystem
+{
+    private readonly World _world;
+
+    public DamageSystem(World world)
+    {
+        _world = world;
+        world.Subscribe<DamageDealtEvent>(OnDamageDealt);
+    }
+
+    public void Update(World world, float deltaTime)
+    {
+        var entitiesWithHealth = world.GetEntitiesWith<AttributeComponent>();
+        foreach (var entity in entitiesWithHealth)
+        {
+            if (world.GetComponent<DeathComponent>(entity) != null) continue;
+
+            var attributes = world.GetComponent<AttributeComponent>(entity);
+            if (attributes == null) continue;
+
+            if (attributes.GetValue(Attribute.Health) <= 0) world.AddComponent(entity, new DeathComponent());
+        }
+    }
+
+    private void OnDamageDealt(DamageDealtEvent e)
+    {
+        var targetAttributes = _world.GetComponent<AttributeComponent>(e.Target);
+        targetAttributes?.ModifyValue(Attribute.Health, -e.Amount);
+    }
+}