Delete bricks that go below the bottom of the play field

core/src/com/me/brickbuster/entity/Brick.java

@@ -78,6 +78,10 @@ public class Brick extends Entity implements PhysicsBody, CollisionListener {
 			hit();
 			hitByBall = false;
 		}
+
+		if (getY() - BRICK_HEIGHT < 0) {
+			delete();
+		}
 	}
 
 	@Override