What a murdoku is and why it hooks you
The puzzle that crosses sudoku with a crime scene: where it came from, exactly how it works and why it is different from a normal sudoku. With free cases to play.
If you have seen a puzzle book in a shop lately with a crime scene drawn on the cover, you have seen a murdoku. The name comes from joining murder and sudoku, and it describes it fairly well: the placement logic of sudoku, set inside a miniature detective story.
The format was popularised by the puzzle designer Manuel Garand, whose book of logic-and-murder puzzles has been circulating for months, and who also publishes free cases on his site several times a week. In very little time it has gone from curiosity to its own shelf in bookshops.
A murdoku is not a sudoku
They share one rule and nothing else. In sudoku you fill in numbers; in a murdoku you place people.
The board is a grid representing a setting — a mansion, a hotel, a theatre — divided into rooms. You have a group of suspects and a victim, and the rules are these:
- Each suspect occupies one cell.
- There can be no two suspects in the same row or the same column. This is the part that comes from sudoku.
- The rooms work like the 3×3 boxes: regions of the board that the clues use to refer to areas.
- And the rule that turns it into a mystery: the murderer is whoever ends up alone with the victim in their room.
The clues are written in plain language. Things like «the countess was north of the colonel», «the butler never set foot in the kitchen», «there were exactly two people in the bar». Nothing gets added up at any point.
That is why, if you come from sudoku, the feeling is odd at first: the technique that serves you is not scanning numbers, it is crossing off possibilities. It sits far closer to classic logic riddles — the «five houses, five colours, five occupations» kind — than to sudoku. Sudoku lends it the board and one rule; the rest is something else.
Why it hooks harder than it should
A well-made sudoku gives a concrete satisfaction: the completed grid. Clean, but abstract. A murdoku gives you a name, and that works differently in your head.
There is a logic to it. By placing named suspects in named rooms, the puzzle stops being a table and becomes a scene you can picture. And since the result is an accusation, the last step does not feel like «I have finished» but like «I have got him». It is the same mechanism that carries any detective novel, applied to a ten-minute logic exercise.
There is also a design detail that helps a great deal: guilt is not an independent fact, it is a consequence. There is no hidden clue saying whodunnit. The name emerges once you have finished placing everybody, which means you cannot cheat by jumping to the end. You have to solve the whole puzzle.
What makes a murdoku good or bad
After generating a fair number of these, three things separate a decent case from a frustrating one:
The solution must be unique. It sounds obvious and it is not. If a puzzle admits two valid arrangements, at some point it forces you to guess, and guessing is not solving. A well-built case can be verified: you walk through every possible arrangement of the board and check that only one satisfies all the clues.
The clues must be pruned. It is easy to write a case with twenty true clues. The problem is that with twenty clues the puzzle solves itself by reading, without deducing anything. A good case carries the minimum number of clues that still leaves it solvable: remove any one of them and it stops having a unique solution.
Negative clues are worth a lot. «Was not in the kitchen» looks weak, but if the kitchen is four cells you have just removed four possibilities. And the best clue in the format is the one saying somebody never entered the room with the body: it rules out a culprit before you have placed anyone.
Murdoku, Murdle and logic grid puzzles
They get confused often, because they arrived at nearly the same time and the covers look alike.
- Murdoku is spatial. There is a map, and the clues talk about positions: north of, next to, in such-and-such room.
- Murdle, by G. T. Karber, uses a classic logic grid: rows of suspects, columns of weapons and places, and you mark ✓ and ✗ at the intersections. There is no map.
- Traditional logic puzzles are the same as Murdle without the criminal framing.
All three train the same muscle — eliminating possibilities until one remains — but they feel different. If you enjoy picturing the setting, murdoku wins. If you prefer the dry pleasure of filling in a table, Murdle.
Where to try it free
At MenteBrillante we have made our own version of the format. We call it Criminoku — the name Murdoku belongs to Garand's book, so we were not going to appropriate it — and we generate the cases ourselves, with a unique solution checked one by one.
- Play the cases in your browser: cases in three levels, free and with no sign-up. It highlights the legal cells as you place, and saves your game if you close the tab.
- Printable cases: six on a sheet, with the solutions at the end. For solving with a pencil, which for this kind of puzzle has its charm.
And if you want a case taken apart from start to finish, with the full chain of deductions, it is in how to solve a murder sudoku.