feat: turrents and explosions

Game/Target/Target.cs

@@ -12,8 +12,9 @@ public partial class Target : Node2D, ITarget
     private readonly Subject<Unit> _timedOut = new();
     [Export] public required Area2D CollisionArea;
     [Export] public required Sprite2D Image;
-    [Export] public double TimeOutDurationInSeconds;
     [Export] public required Timer TimeOutTimer;
+    [Export] private PackedScene _explosionPackedScene = null!;
+    [Inject] private ILevel _level = null!;
 
     [Inject] private ITargetCollector _targetCollector = null!;
 
@@ -25,7 +26,8 @@ public partial class Target : Node2D, ITarget
     {
         Image.Visible = true;
         CollisionArea.Monitoring = true;
-        TimeOutTimer.Start(TimeOutDurationInSeconds);
+        CollisionArea.Monitorable = true;
+        TimeOutTimer.Start(_level.SpawnDuration.TotalSeconds);
     }
 
     public override void _Ready()
@@ -39,18 +41,29 @@ public partial class Target : Node2D, ITarget
         _hit.Dispose();
     }
 
-    // todo: hook to collision
+    private void OnAreaEntered(Area2D _)
+    {
+        OnHit();
+    }
+
     private void OnHit()
     {
         Disable();
         TimeOutTimer.Stop();
         _hit.OnNext(Unit.Default);
+
+        var explosion = (GpuParticles2D)_explosionPackedScene.Instantiate();
+        explosion.GlobalPosition = GlobalPosition;
+        explosion.Emitting = true;
+        GetTree().CurrentScene.AddChild(explosion);
     }
 
     private void Disable()
     {
         Image.Visible = false;
-        CollisionArea.Monitoring = false;
+        // can't se monitoring/monitorable when inside the collision code, like during OnHit
+        CollisionArea.SetDeferred(Area2D.PropertyName.Monitoring, false);
+        CollisionArea.SetDeferred(Area2D.PropertyName.Monitorable, false);
     }
 
     private void OnTimeout()