Man, this took me back. Just stumbled through the first two levels and will have to come back to the others when I have some more time.
I love an educational game. This one does seem to be a little all over the place in terms of difficulty and the expectations you put on the player. Concepts are presented without clear definitions or explanations, just formulas, so I assume the target audience is calc students who are reviewing known material. But the questions themselves would be pretty trivial for anyone who already knows the material to the level you're expecting. (slope of x^2, area of rectangle [2;0] x [0;5], etc) Edit: Then again, the time pressure makes even the simple questions much more difficult! I like that the boss fight is a more involved, multi-step question.
The formulas themselves could be presented better. I had a really hard time just visually parsing something like this:
∫_0^1 dx ∫_x^1 f(x;y) dy = ?
I eventually figured out what was going on here but if you could get some latex like formulas working in here it'd be so much nicer.
I say all of this but I haven't touched a calc textbook in a million years so I was remembering how all this machinery works on the fly. Overall I had fun waking up some long-neglected parts of my brain for this one and would definitely play more.