A friend of mine from state math team, Luyi, has a really neat geometry blog. She just linked to a game I've been trying to refind for years called Planarity. Read her comments about it here.
Planarity, in principle, is a really simple game. You get a circle of dots - vertices. Each is connected to anywhere between 2 and 5 other points with lines - edges. All you have to do is move the dots so that none of the edges cross. It's very tricky, and very fun. At the moment, I'm up to level 8.
The Boston Projection
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