How to Play Detective Sudoku: The Complete Cluedoku Rules Guide

The Grid and the Rooms

Every Cluedoku case starts on a square grid, anywhere from a compact 4x4 on the earliest campaign cases up to a 10x10 for the hardest expert cases. The grid is not one open floor plan, it is carved into several irregularly shaped rooms with names like Kitchen, Library, Bedroom, and Gallery, and each room covers a cluster of cells rather than a neat rectangle. Learning the room boundaries before you touch a clue is worth the extra minute, since almost every witness statement in the game refers back to a room.

Some cells also hold objects, and they behave in three distinct ways. Blocking objects, things like a table, wardrobe, TV, statue, bookshelf, piano, fireplace, fountain, column, or sunflower, take up their cell completely, so no suspect can ever stand there. Floor objects, like a carpet or rug, are just decoration on the floor, and suspects can stand right on top of them. Furniture such as a chair, bench, or stool sits on top of a floor object, and a suspect can occupy that cell too, so one square might hold a rug, a chair, and a suspect all at once.

Objects matter beyond scenery. Several clue types reference them directly, and blocking objects quietly shrink the pool of cells a suspect could occupy, often your first real foothold into a new case.

Suspects, the Victim, and the Sudoku Rule

Every case has a set of suspects labeled A, B, C and onward depending on the grid size, plus one more figure marked V for the Victim. Each of them occupies exactly one cell on the board, and that is where the sudoku half of Cluedoku kicks in: no two suspects, the Victim included, are ever allowed to share a row or a column. That single rule does a huge amount of work on its own, because placing one suspect immediately rules out an entire row and an entire column for everyone else.

The Victim is not just another figure to place, they are the reason you are solving the case at all. The Victim was alone with the killer, which means V shares a room with exactly one other suspect, and whoever that turns out to be is the murderer. Every other suspect can share a room with as many people as the clues allow. Only the Victim's room is restricted to precisely one companion.

Put those two rules together, one row and column per suspect, one roommate for the Victim, and there is always exactly one arrangement that satisfies every clue on the board. That guarantee is what makes Cluedoku a logic puzzle rather than a guessing game. Follow the deductions correctly and you will find the killer, not just a killer.

Reading a Clue

Every suspect except the Victim comes with one clue, written as a plain witness statement instead of a coordinate or a formula. Some clues are about rooms outright: "He was in the Kitchen" means that suspect's cell has to fall inside the Kitchen, while "She was NOT in the Gallery" does the opposite and crosses out every Gallery cell for her.

Other clues describe a suspect's relationship to an object or to the room's architecture. "He was on a carpet" narrows him down to floor-object cells. "She was beside a table" puts her in a cell directly next to a table in the same room. "He was at a wall" means his cell touches that room's outer boundary, and "She was in a corner" means at least two of the room's walls meet at her cell. Each of these trims a suspect's list of possible cells, sometimes down to just a handful.

The most powerful clues mention other suspects by name. "He was with Diana in the Library" ties two suspects to the same room at once, so any deduction about one of them narrows the other too. "She was alone with Boris" is stricter still, it means exactly those two people were in that room and nobody else. A few clues are not tied to any single suspect at all: "Exactly 3 people were in the Ballroom" and "The Cellar was locked, nobody inside" are case-wide rules that govern a room no matter who you are currently reasoning about.

How to Solve a Case, Step by Step

1. Read every clue before placing anything. Go through all the witness statements once and note what each one rules in or out, including the case-wide rules about exact head counts or locked rooms, since those apply even to suspects without a personal clue.
2. Pencil-mark every suspect's possible cells. For each suspect, mark every cell that is not already ruled out by their own clue, by a blocking object, or by a case-wide rule. Some suspects will already be down to just one or two candidates.
3. Apply the row and column rule. Once candidates are narrow, check whether any row or column has only one suspect who could possibly go there. If so, place them, then immediately cross that row and column off every other suspect's remaining candidates.
4. Cross-reference the social clues. Clues naming two suspects only resolve together: if a "with" or "alone with" clue narrows one suspect's room, apply that same room to their partner, and if someone "was alone," clear every other suspect out of that room. Keep cycling through these steps, since each placement tends to free up a new deduction elsewhere, until every suspect has a cell, the Victim has exactly one roommate, and that roommate is your killer.

Tips for Faster Solving

• Start with the most restrictive clues first. A suspect who is "in a corner" or "beside a table" usually has far fewer candidate cells than one who is simply "in the Kitchen," so solve those first and let the row and column rule cascade outward from there.
• Handle exact-count and locked-room rules before anything else. A clue like "Exactly 3 people were in the Ballroom" or "The Cellar was locked, nobody inside" applies to the whole room at once, so use it to cross off cells before you even look at anyone's individual clue.
• Keep your pencil marks current. Every time you place a suspect, revisit the candidates for everyone else sharing their row, column, or room. One placement often cascades into two or three more.
• Solve paired clues together. When a clue names two suspects, "with" or "alone with," narrowing one half usually narrows the other for free, so tackle the pair as a unit.
• Work backward from the Victim once the board thins out. Once you know which room V ends up in, whichever suspect is left with a valid cell there is your murderer, often the fastest way to close out the last few placements.