How to play
1. Probe
Type any sequence and the game tells you whether it FITS the secret rule or FAILS it. Probes are your score, so waste as few as you can.
2. Commit
When you think you have it, build the rule itself out of tokens. You get three commits.
3. Be judged on behaviour
Your rule is right if it accepts and rejects exactly what the secret rule does. "Every gap is positive" is accepted when the answer was "every term is greater than the one before it". They are the same rule.
4. Beat par
Par is what a perfect player needs: at every step, the probe that splits the remaining possibilities most evenly. Finish under it and you outplayed the solver.
Three hints per puzzle, escalating. The first names what the rule is about. The second hands you a sequence worth testing and tells you what it comes back as. The third gives up one word of the answer.