add update method to code blocks for clarity

content/pong/ball/bouncing/motion_engine.md

@@ -81,8 +81,8 @@ Next, in a separate block, let's consolidate our MotionMessages per Entity.
 
     private readonly Dictionary<Entity, Vector2> _moveAmounts = new Dictionary<Entity, Vector2>();
 
-    ...
-
+    public override void Update(double dt)
+    {
         _spatialHash.Clear();
         _moveAmounts.Clear();
 
@@ -236,6 +236,8 @@ namespace PongFE.Engines
 Now, in the final block of our **MotionEngine**, we can perform our collision tests and send out our messages.
 
 ```cs
+    public override void Update(double dt)
+    {
         ...
 
         foreach (var entity in TrackedEntities)
@@ -276,6 +278,7 @@ Now, in the final block of our **MotionEngine**, we can perform our collision te
 
             SendMessage(new UpdatePositionMessage(entity, projectedPosition));
         }
+    }
 ```
 
 Here, we go over everything with a Position and Collision component, sweep test for collisions, and send appropriate Collision and UpdatePosition messages accordingly.