public void AddLayer(Texture2D picture, float depth, float moveRate)
        {
            BackgroundLayer layer = new BackgroundLayer();

            layer.picture       = picture;
            layer.depth         = depth;
            layer.moveRate      = moveRate;
            layer.pictureSize.X = picture.Width;
            layer.pictureSize.Y = picture.Height;
            layerList.Add(layer);
        }
 public int CompareDepth(BackgroundLayer layer1, BackgroundLayer layer2)
 {
     if (layer1.depth < layer2.depth)
     {
         return(1);
     }
     if (layer1.depth > layer2.depth)
     {
         return(-1);
     }
     if (layer1.depth == layer2.depth)
     {
         return(0);
     }
     return(0);
 }