Really nice site. Well done. The example problem that showed up to me (equilibrium point detection) was not trivial, but didn't require advanced stuff which a halfway decent programmer wouldn't use day in and day out.

I also like the way you tell me what you scored on and what my result was.

I wonder if you should relax the condition that you can submit only once.

I gather TopCoder offers something similar. What's your strategy to compete with them?

PS: got 94 using C++ in 16 min b/c I didn't check overflow of large numbers. Good thing you check for that.