I have recently started playing around at CodinGame, and I have been enjoying myself enough that I felt the need to share. The site generally falls under the development e-learning category, but stretches to a whole new level. After setting up an account, you can start by diving right into the many code puzzles available.
After checking out the practice puzzles, its time to see the rest of what CodinGame has to offer. My favorite is the competitions, which are generally broken down into bot programming, code golf, and optimization puzzles. While the code golf and optimization puzzles give you a score to rank on the leaderboard, the bot programming games will pit your code directly up against other users – assigning you a score and rank that allows your bot to progress through leagues. In addition, CodinGame occasionally hosts timed competitions that include various prizes. Users can also allow potential employers to see their progress in these competitions directly through the site, to help discover new employment opportunities.
The site also offers a great way to track progress across the various puzzles, competitions, and arena games through the use of experience, levels, and achievements. After spending a decent amount of time on the site, the site ranks me 3,425th in the world (out of 717,981) – and 262nd in the US (out of 135,699). Come give it a shot, and see how you fare.