Looks and sound great, the chess scenarios where fun too, I enjoyed playing this!
The main mechanic did seem a bit underutilized though. I realised that it was much more effective to run down your opponent's clock by quickly making aggressive moves, since they'd waste their entire time limit on defending. Maybe the opponents could be adjusted to use less time during their turns if the player hasn't cheated in a while?
Regardless, this is still very well made. Great work!