I'm generally against competitive anything though I may be the outlier of all outliers in this regard.
I was on one job where things were so rushed that I overlooked the simplest solution to a thorny problem, rsync.
I do prefer cooperative things.
You know, what we're told in school to be cheating and punished for, is how we get things done.
tldr; math practice site with elo-based ranking, physics problem simulations, teaching interface. feedback greatly appreciated!!