anchor.diff:     * Gets the context(State) in which the Sprite was created.
      */
     State get context => _context;
  -  
  +
     /**
      * Set the horizontal and vertical speed with the same value.
      */
  -  void set speed(num speed){
  +  void set speed(num speed) {
       speedX = speed;
       speedY = speed;
     }
  -
  -  /**
  -   * Rotate the sprite in radians.
  +  
  +  /**
  +   * Set the horizontal and vertical acceleration with the same value.
  +   */
  +  void set acceleration(num acceleration) {
  +    accelerationX = acceleration;
  +    accelerationY = acceleration;
  +  }
  +
  +  /**
  +   * Rotate the sprite and it's direction vectors in radians.
      */
     void rotateRadians(num radians) {
       rotation += radians;
  
positive.code:    * */
    num speedY = 0;
  
    StageXL.Vector mainDirection = new StageXL.Vector.zero();
  
    StageXL.Vector upDirection = new StageXL.Vector(0, -1);
  
negative.code: 
      x = x + mainDirection.x * speedX * time;
      y = y + mainDirection.y * speedY * time;
      print('$speedY');
  
      return true;
  
  