Nine puzzles, daily.
A fresh set every UTC midnight. Sweep all nine for a perfect day and keep your streak alive.
Today's puzzles
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Why UTC?
Everyone everywhere sees the same daily puzzle on the same calendar date — no advantage to playing at midnight in your timezone.
Next reset: in
Guess the Output
We show you a snippet. You guess what it prints. Sounds easy. It isn’t.
Accepted Answer
Four answers. One is correct. The others look suspiciously confident.
Spot the Bug
Working-looking code with one nasty gremlin. Click the line that lies.
Regex Roulette
Match these strings. Reject those. Shortest regex wins.
Code Golf
Solve the problem. Use the fewest characters. Par is just the beginning.
Type Signature
Read the TypeScript. Guess the type. The compiler knows — do you?
Time Complexity
One algorithm. Four Big-O options. Only one is right.
Dependency Detective
A real package. Four descriptions. The npm ecosystem is wild.
Which Language?
One snippet. Four languages. Read the syntax — pick the tongue.
Staff pick · Guess the Output
The launch-day classic. Start here if you’re new.