ILLEGAL: n b8-a6 on turn 3:
There was no n on b8. The piece on b8 is a q.
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For diagnostic purposes, here is the full movelist:
1. P e2-e4 
1... p d7-d6 
2. P d2-d4 
2... p c7-c5 
3. P f2-f4 
3... n b8-a6 
4. P b2-b3 
4... c h8-g6 
5. P f4-f5 
5... c g6-h8 
6. N c1-d3 
6... p f7-f6 
7. N d3-f4 
7... n a6-c7 
8. P d4-d5 
8... a g8-h6 
9. DH g1-e3 
9... p g7-g5 
10. N f4-e6 //Check!
10... n c7-e6 
11. P f5-e6 
11... s a8-c7 
12. P h2-h4 
12... p f6-f5 
13. A f1-c4 
13... p b7-b5 
14. A c4-b2 
14... k f8-g7 
15. k g7-f8 //Illegal move, please make another one.
15... c h8-g8 
16. P h4-g5 
16... a h6-g4 
17. C h1-h7;won //Checkmate!
In case there is a bug in the code, the settings file can be edited at /play/pbm/play.php?game=Cetran+Chess+2&settings=asymmetric&submit=Edit