There’s a simple way to learn geometry over the summer. It is easy and fun. Imagine Euclidean geometry: the video game. If your experience in high school geometry was anything like mine, it probably sounds like torture. But games make learning fun.

http://www.forbes.com/sites/jordanshapiro/2014/05/24/if-euclid-played-video-games-this-is-the-app-hed-build-to-teach-geometry/