Hidden Rule

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Test numbers to find the day's hidden rule, then prove it in one final exam.

Play Hidden Rule

on hidden-rule-game.com

Hidden Rule Day 46 on a desktop: 510, 615 and 906 marked YES, a test of 150 answered YES, par 11

Hidden Rule is a daily number deduction game. You start with a few numbers that follow a secret rule, test any number from 1 to 999 to see whether it fits, and when you think you know the rule, you prove it by sorting a final set of numbers into YES and NO in a single submission.

About Hidden Rule

Hidden Rule plays like the classic 2, 4, 6 task from psychology. Each day opens with three numbers that follow the hidden rule, such as 36, 412 and 949. You type any number from 1 to 999 and press Test, and the game answers YES or NO. Rules use divisibility, digits or size, sometimes joined by AND or OR.

Fewer tests score better, and each puzzle has a par, a target rather than a limit. A list of your tests can be filtered and sorted to spot the pattern, and a hint is available at the cost of marking your result. The game's own advice is to test a number that could prove your theory wrong.

When you stop testing, the second stage begins: a set of numbers to mark as fitting the rule or not, with one submission. Each day is numbered, there is an archive of earlier puzzles, stats and a streak, and a practice puzzle teaches the game. It suits players who like logic puzzles about patterns rather than grids.

How to play Hidden Rule

Look at the numbers that already follow the day's rule.
Type a number from 1 to 999 and press Test to see whether it fits.
Keep testing to narrow the rule down, ideally within par.
Press Prove your rule and mark each number in the final set YES or NO in one submission.

Screenshots

Hidden Rule Day 46 on a phone: the three starting numbers, a test of 151 answered NO and the Prove your rule button

Hidden Rule share card: A daily deduction game, with the numbers 2, 4 and 6

Tips

Test numbers that would break your current theory, not ones that confirm it.
Check digit rules and divisibility separately: try a number with the same digits in another order.
Use the filter to view only YES or only NO results when the list grows.