anchor.diff:      node.position.y += speed.y * dt;
       speed.x += acceleration.x * dt;
       speed.y += acceleration.y * dt;
  -
  -    if (collideWorld){
  -      _correctForWoldCollision();
  -    }
  -  }
  -
  -  void _correctForWoldCollision() {
  -    if (position.x < world.left) {
  -      position.x = world.left;
  -      speed.x *= -bounce.x;
  -    }
  -
  -    if (position.x > world.right) {
  -      position.x = world.right;
  -      speed.x *= -bounce.x;
  -    }
  -
  -    if (position.y < world.top) {
  -      position.y = world.top;
  -      speed.y *= -bounce.y;
  -    }
  -
  -    if (position.y > world.bottom) {
  -      position.y = world.bottom;
  -      speed.y *= -bounce.y;
  -    }
     }
   }
   
  
positive.code: 
  part of cocos;
  
  class PhysicsComponent {
    GameNode node;
    World world;
  
negative.code:     position = new Vector2(x, y);
      size = new Vector2(width, height);
    }
  
    void update(num dt) {
  
    }
  }
  