public SlideOverTransition(SlideOverTransitionDirection direction = SlideOverTransitionDirection.North)
 {
     this.direction          = direction;
     this.progress_per_frame = 1.0 / 15.0;
 }
 public SlideOverTransition(SlideOverTransitionDirection direction = SlideOverTransitionDirection.North)
 {
     this.direction = direction;
     this.progress_per_frame = 1.0 / 15.0;
 }