Wow, if I had a week of time and was told to make a chess game, I probably wont finish in time.
Some critique:
1) You forgot to disable movable separator in the endgame screen (between "X wins" and "Replay; Exit")
2) If white wins and "Replay" is pressed, then black move first :D
3) Game sometimes just randomly crushes.
Here is an opening that leads to a game crush.
1. e4 c6 2. Kc3 d5 3. d4 Kf6 4. e5 Kfd7 5. f4 c5 6. Be3 Kc6 7. Qf3 (game crash)!?
Here is another one:
1. e4 e5 2. Kf3 Kc6 3. d4 e:d4 4. K:d4 Bc5 5. Bc4 (game crash)!?
Those are very consistent and easy to reproduce btw.