anchor.diff:     *
      * Direction can be: up/forward, down/backward, left, right
      */
  -  move(String direction) {
  +  void move(String direction) {
   
       _newDirection = mainDirection;
   
  
positive.code:   /**
     * Removes the sprite from the world and juggler.
     */
    removeFromWorld() {
      alive = false;
      _context.game.world.removeChild(this);
      if (isMovable) {
  
negative.code:   /**
     * Sprite will be added to the world and to the juggler if the sprite is moveable.
     */
    void addToWorld() {
      alive = true;
      _context.game.world.addChild(this);
      if (isMovable) {
        _context.game.world.juggler.add(this);
  