ILLEGAL: s f8-e8 on turn 18:
There was no s on f8. The piece on f8 is a q.
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For diagnostic purposes, here is the full movelist:
1. P e2-e4 
1... p e7-e5 
2. DH d1-g4 
2... n d8-e6 
3. P f2-f3 
3... p h7-h5 
4. DH g4-g3 
4... n e6-f4 
5. P c2-c3 
5... p a7-a5 
6. DH g3-f2 
6... r h8-h6 
7. A a1-b3 
7... p b7-b6 
8. N c1-d3 
8... a b8-a6 
9. DH f2-e3 
9... dh a8-c6 
10. K f1-f2 
10... p g7-g5 
11. P g2-g3 
11... n f4-h3 //Check!
12. K f2-g2 
12... n h3-g1 
13. K g2-g1 
13... r h6-g6 
14. K g1-f2 
14... p d7-d6 
15. C e1-g2 
15... dh c6-b5 
16. K f2-e2 
16... dh b5-c4 
17. A b3-a4 
17... dh c4-a2 
18. A a4-e8 
18... s f8-e8 //f8-e7-e8
19. R b1-f1 
19... dh a2-b2 
20. K e2-f2 
20... dh b2-c2 
21. N d3-e1 
21... dh c2-b1 
22. P h2-h4 
22... p g5-g4 
23. P f3-g4 
23... q c8-g4 
24. DH e3-f3 
24... r g6-f6 
25. S h1-h2 
25... a a6-c5 //Check!
26. K f2-g1 
26... K g1-f2 //Illegal move!
27. K f2-e2 
27... s e8-e4 //Check!
28. K e2-d1 
28... a c5-b3 //Check!
29. resign
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