-void applyCollision(PhysicsEntity* p1, PhysicsEntity* p2);
-void applyCollision(Ball* b1, Ball* b2);
-void applyCollision(Polygon* pPoly, Ball* pBall);
+static void applyCollision(PhysicsEntity*, PhysicsEntity*);
+static void applyCollision(Ball*, Ball*);
+static void applyCollision(Polygon*, Ball*);