Easy
Three terms, 1 to 30. A gentle vocabulary and par of two to five probes.
Play →Guess the rule, not the answer.
Rularoo is a daily deduction game built on Peter Wason's 2-4-6 task, the experiment that showed people look for evidence that confirms them and almost never for evidence that would prove them wrong.
Today the game opens with something like
Most people guess "add two each time". Most people are wrong, and every test they run says FITS.
The rule people reach for is almost always narrower than the real one. A narrower rule only accepts sequences the real rule also accepts, so every sequence you test to confirm your idea comes back FITS. Confirmation cannot get you out. The probe that frees you is one you expected to fail.