The Bugdle Big-O archive is a complete index of every daily time-complexity puzzle ever published. Each entry presents a short, self-contained snippet — typically four to fifteen lines, in a mainstream language — and asks the player to name its dominant complexity from an eight-class ladder running from O(1) up to O(n!). Four guesses, with a directional “higher / lower” hint after every miss; the ladder is totally ordered so the puzzle is solvable in three perfectly-read guesses (plus one buffer for misreads).
The catalog deliberately rotates through the recognisable shapes you'd see in a code review: single loops, nested loops with bounded inner counts, divide-and-conquer recursions, amortised data-structure operations, naive subset and permutation generators. Most working engineers can producea complexity analysis; far fewer have the recognition instinct to read someone else's code and judge its growth at a glance. The archive is designed to train that instinct. Every postmortem unpacks the dominant loop, the common confusables that mislead first-time readers, and the one heuristic that would have nailed the answer immediately.