Why in the hell are you not adding the missing undu button?

It is really annoying to play for more than an hour and loose because you accidentally swipe your finger to the wrong direction. There should be an undo button that rewinds the last move. I dont expect undoing mire than the last step. The sad thing is that this option exists in other mobile device systems (you know). Why dont you add it to the iOS version? Why? It is not fun anymore.

Snowdrop Apple about 2048, v2.0