The top-voted answer is Racetrack: "In the game of Racetrack, cars race around a track bounded by two concentric closed loops drawn on a square grid. Implement a program that plays this game."
It's time to choose a community-challenge for August 2015.
- Post your challenge as an answer to this question. Feel free to resubmit non-winning ideas from previous months.
- Vote for those answers which interest you.
- At the end-of-day on Friday, July 31st, the top-voted post will become the next challenge.
Once the challenge topic is decided, post your solution as a question on the main site and tag it with community-challenge. The challenge runs throughout August (but nothing stops you from posting an entry later on).