Same as TheRandomDot, BUT...
I got the same problem with Firefox, but when I tried Chrome, it worked well... That means, NEXT button appeared in the lower right corner as it should, but with Firefox, it didn't...
And I found 2 more glitches:
1) While fighting the Hun, when I killed the two foot ninjas and he ran towards me, I used special attack with Casey Jones, he got stuck in the same position and I couldn't kill him. I had to restart the level.
2) While fighting the Shredder in the last level, he jumpslided to the right acid tank and got stuck at the edge, so I could finish him off easily....
Otherwise, the game was really good- balanced gameplay, good story, not too hard but challenging, nice music. I would give 10, but for glitches (especially the one with Firefox, it can really ruin the whole thing to some people) I can't. Fix them and it will be great game. PM me if you need more specific info on my system configuration to fix it and keep up the good work! :-)