game now more compatible for mobile users. more work required still

Use variables for these - that way you can do something like
@playerSpriteSize : 100px;
background-size: @playerSpriteSize*3 @playerSpriteSize;
//and to shift the sprite:
background-postiion: @playerSpriteSize * -1 0;
background-postiion: @playerSpriteSize * -2 0;
That way, if you decide to change the dimensions everything just works out neatly