An interesting challenge: Create a complete game in under 1 hour. See the results and code here.
William at PhaserGames.com published the results of a fun little challenge: Create a game in under 1 hour: "Sometimes I want to challenge myself to write a game in just 1 hour. Obviously, this does limit what games I can make, but that doesn’t mean the game is just an experiment. My brothers and sisters and I would fight over the Simon Game when I was a kid. If you are too young to know what it is, it was a big plastic circle with 4 buttons that would light up, and you’d have to match the pattern of the song it played."