Hi!

So I'm updating Twisty Chess. 

So what's new?

- An undo button

- A known bug with the undo button that sometimes makes it problematic to undo beyond a switch move. Just try not to do it.

- Removed castling currently, having problems with it. I will add it back in the next version.

- Fallen tiles: a feature that allows you to leave behind a tile no one can enter to.

I still haven't added AI. Will add it to the next version.

If you find any bugs, let me know.