Play on turbo for the best experience. Don't play on turbo if you like seeing the valid spaces pop up as they are generated. Incomplete, every piece should work correctly, but there are no game states, so players can move twice in a row, it doesn't stop when a king is dead, nor does it prevent checkmates. Frankly with the current system, preventing checkmates would be... slow.
Curse you, @redairplane, for afflicting my brain with the idea of 5x5 chess at least 6 years ago. Maybe now that it is created, I can sleep soundly.