anchor.diff:    void rotateDirectionsRads(num radians) {
       directionSystem.rotateDirectionsRadians(radians);
     }
  -  
  +
     StageXL.Vector getVelocity() {
       return directionSystem.mainDirection.scale(speed);
     }
  
positive.code:   /**
     * Speed of gravity.
     */
    int speed = 0;
  
    /**
     * Gravity's [DirectionSystem].
  
negative.code: 
    /**
     * Set the gravity's direction to zero vector.
     *
     * This means the gravity wont have a direction and this means there will be no gravity.
     */
    void nullDirection() {
  