Guess the Rule

Yes, and it's built into the code. Every puzzle, the engine first finds a rule strictly narrower than the real one, and draws both examples from it. Using the classic 2-4-6 as an analogy: if the real rule were "ascending order", the examples might happen to be exactly 2, 4, 6 — which also satisfy the much narrower "add 2 each time". Since the narrow rule sits entirely inside the real one, any card that fits it always answers "fits" too. That's not a trick on you personally — it's the exact thing the game wants you to run into. The reveal names the narrow rule today's puzzle drew you toward.

A 1960 experiment by British psychologist Peter Wason. Subjects were told the sequence 2, 4, 6 fit a rule in his head, and could propose their own triples to test before announcing their guess. Most people quickly guessed "add 2 each time", tested 8-10-12 and 20-22-24, got "fits" every time, and confidently announced their answer — wrong. The real rule was just "ascending order". The problem wasn't intelligence; it was that every test they ran was one their own guess predicted would fit, and that kind of test can never prove you wrong. A useful test is one your own guess predicts should FAIL, like 1-2-3 or 6-4-2. This game puts that experiment on cards, plus something the original never recorded: which side you bet on, every single time.

Confirmation bias is the tendency to look for evidence that supports what you already believe, rather than evidence that could disprove it. It's hard to see from the outside: two players can run the same number of tests and get nearly the same number of "doesn't fit" answers back (0.2 vs 1.6 per game in simulation) — what actually differs is what they expected going in. That's why posting through a slot IS the bet. The reveal's ledger — "bet fits 9 times, bet doesn't fit 0 times" — is what this run's testing strategy actually looked like, in your own numbers. It measures the run, not you.

A surprise is when your bet doesn't match the box's answer — you post through "won't fit" and it lands in the fits pile anyway. The card visibly crosses to the other side, flips to a bone-white face, and gets a heavy exclamation mark. It's built that way because a card that lands where you expected only reinforces a theory you already had; one that surprises you actually rules a wrong theory out. That's exactly what a real experiment is for. More ❗ marks, especially early, usually means a faster crack.

A failed exam flips the wrong cards to their true answer and adds all eight to your evidence, and the count goes up by "8 plus the number you got wrong". It's 8 because the moment you submit, you've effectively seen eight answers — and they were chosen specifically to expose the wrong theories a player would likely hold, which makes them more informative than cards you'd post yourself. We simulated the alternatives: a flat +3 penalty lets a player who never tests, just declares immediately and mines the exam's answers, beat an honest tester on 99.7% of puzzles; 8 plus wrong-count brings that down to 0%. Missing one card also costs less than a wild guess — that asymmetry is intentional too.

Your local calendar date is the seed, so everyone in the world gets the same rule, the same examples and the same exam on the same day, and it never repeats on consecutive days. Sharing only sends the date, a string of ⚪⚫❗ symbols, and a count — never the rule's text, so it's safe to post in a group chat. Practice mode draws a separate puzzle at a difficulty tier of your choice and never touches the daily streak.