Deduce — a free daily murder-mystery logic grid. Every case is solver-verified, so there's exactly one answer and it's always reachable by pure deduction.
Posting this with the mod team's go-ahead — I messaged first under rule 5.
I build a free daily deduction puzzle called **Deduce**. One case a day: a victim, a set of suspects, a set of rooms and a set of weapons, plus a list of clues you eliminate on a grid until one combination survives. Name who, where, and with what.
**The bit I think matters for this sub:** every case is machine-verified before it publishes. A constraint solver checks two things — that exactly one solution exists, and that it's reachable by pure deduction. If the answer can only be found by trial and error, the case is thrown away and regenerated. You should never have to guess, and if you ever do, that's a bug rather than a design choice.
Five tiers. The first four are 4×4×4 grids with 6–13 clues. The top tier, **Grand Sleuth**, is 5×5×5 plus a fifth axis — each suspect's arrival time — which is the full six-block staircase grid, with 17–18 clues. Some of those clues are deliberate lies you have to catch by contradiction.
How people are actually doing, of those who commit to an accusation:
| Tier | Solve rate |
| Junior | 79% |
| Inspector | 74% |
| Master Detective | 74% |
| Grand Sleuth | 61% |
Just over 1,750 cases solved so far across 204 registered detectives and a lot more anonymous ones. Four different settings, so the cast changes.
Free, no account needed to play, no ads, nothing to buy, runs in the browser. An account only exists to track your streak and unlock the higher tiers.
- Today's case: https://deduce.studio/daily
- Archive of closed cases (no solutions): https://deduce.studio/archive
Full disclosure: I built it solo, in my evenings. Happy to answer anything about how the generator or the verifier works — and genuinely happy to hear where it's too easy, too hard, or unclear.