I didn't intend to, but I played the whole thing in one session, I got so into it!
The concept is great and works really well, but the game is also very well polished and thought out, great job.
The difficulty balance is almost perfect. A few of the puzzles had me scratching my head, but I was never frustrated.
My only critique is that the sound that plays when you get to promote a pawn doesn't really work for me. It doesn't go with the music, and is a bit jarring. That's it, though. Other than that I loved it!
I also really appreciate the mobile support, it works well with a touch screen.