I've done some game programming on TI calculators and I'll tell ya, it's not impossible to make a decent game with it, but not via the TI programming language. You have to program it in assembly. There are already games like mario and this game called squrxz or some crazy name that was like a platformer with some alien headed character and you could even make your own levels with it and the game itself had tons of complex levels.
But scripting it directly in the calculator... you can only make games out of text or the symbols on the calc... I made a decent racing game but it was like
NPC Code:
I ' ' I
I ' 8 ' I
I ' 8 ' I
I ' ' I
I ' ' I
Like the I's were the border and the 8's were the cars and the 's were the road lines... That is about as good as it's gonna get.