forgot to define BounceMessage

content/pong/ball/bouncing/collision_dispatch.md

@@ -30,6 +30,28 @@ namespace PongFE.Components
 }
 ```
 
+We'll also need **PongFE/Messages/BounceMessage.cs**:
+
+```cs
+using Encompass;
+using PongFE.Components;
+
+namespace PongFE.Messages
+{
+    public struct BounceMessage : IMessage, IHasEntity
+    {
+        public Entity Entity { get; }
+        public HitOrientation HitOrientation { get; }
+
+        public BounceMessage(Entity entity, HitOrientation hitOrientation)
+        {
+            Entity = entity;
+            HitOrientation = hitOrientation;
+        }
+    }
+}
+```
+
 In **PongFE/Engines/CollisionEngine.cs**:
 
 ```cs