Nitpick, but elevation would make much more sense if you assumed a base plane + set a perspective, and then translate3d'd upwards on the Z axis. It would grow the size of the element as well.

Saying that, probably annoying to work with transformed DOM nodes, but the background being the only thing moving in the "bounce" example just stood out to me as weird.

Also, the texures seem to be just gradients or embedded texture data. Was thinking this would use https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/V... and fall back to gradients/premade images for firefox.