anchor.diff:    State _context;
   
     /**
  -     * Does the sprite move?
  -     */
  +   * Does the sprite move?
  +   */
     bool isMovable;
   
     /**
  
positive.code:  * 1. You can just make one Sprite object. This is a good way for making simple 
   * Sprite object. For example: bullets
   * 2. You can extend the Sprite class and make your very own Sprite object. It's
   * good for making more complex Sprite objects. For example: player, ufo
   * 
   * Examples:
   *      //First case
  
negative.code:           isMovable: isMovable);
  
    /**
     * Defines where the sprite will move next.
     */
    bool advanceTime(num time) {
      if ((x <= 0 || x >= _context.game.world.width) ||
  