Crossword puzzles whose clues are regular expressions, starting gentle and ending somewhere near cruel. The most painless way to actually learn the syntax.
Hundreds of maths problems you can only solve with code, where the brute-force answer takes a week and the clever one takes a second.
A December calendar of programming puzzles with a story, a leaderboard and a devoted community.
Thousands of jigsaw puzzles uploaded by the community, from a dozen pieces to a few thousand, playable in the browser.
Daily estimation games: guess how big, how far or how many, and see how close your gut feeling gets to the real number.
Counter-Strike-style surfing in a browser tab: fifteen classic maps, proper Source air-strafing and global leaderboards for every run.
Measure your reaction time, visual memory and number recall in short tests, then see where you land against everyone else.
