About Prime Suspects

Prime Suspects is a noir deduction game disguised as a maths toy. Twelve numbered suspects stand in a lineup. One of them did it. You have five chips and a handful of probe cards, and every probe asks exactly one true question about the culprit — is it a perfect square, does it wear a seven, is it prime, literally. Whatever the answer, every suspect standing on the wrong side of it walks out of the room.

How a case plays

A case runs in three beats. In the draft, eleven probe cards hit the felt and you keep six. Beat cops are blunt instruments. Detectives ask the classic questions. Specialists are surgical. Wildcards bend the rules. In the interrogation, you spend chips to play those probes; the culprit answers honestly, the dossier records the fact, and the lineup thins. In the accusation, you name a survivor and slam the stamp. The right name closes the case. The wrong one clears your streak.

Par

Printed beside the chips is par — the number of chips an optimal interrogation would need for that specific lineup, computed by a balanced-split solver before the case is dealt. It is not a guess or a fixed difficulty setting; it is the actual answer for the actual case in front of you. Beating par means you found a line of questioning as efficient as the solver did.

The idea

Underneath the felt and the gold lettering, this is binary search wearing a hat. The best probe is the one that splits the room closest to in half, and the game rewards that instinct without ever naming it. It came out of a suspicion that the reason people find this kind of reasoning cold is presentation, not content — that the same puzzle framed as an interrogation is simply better company than the same puzzle framed as an exercise.

It is free, MIT-licensed, runs entirely in your browser, and needs no account. The source is on GitHub.