Dedoku: Deduction Detective

Dedoku: a Detective Puzzle Game Built on Sudoku Logic

Dedoku is a free online detective puzzle game where every case is solved by deduction. Instead of filling a grid with numbers, you place witnesses and a missing case item into a building. The familiar Sudoku idea is still there: each case piece can appear only once in each row and only once in each column. The mystery twist is that the rest of the answer comes from clues about rooms, objects, directions, and who could have found the missing item.

The result is a logic detective game with the feel of a case file. One puzzle might send you through a grand hotel looking for a trophy, while another might hide a diamond in a museum gallery or a golden key in a castle wing. The theme changes, the clues change, and the floor plan changes, but the important promise stays the same: the case should have one answer, and guessing should not be required.

How Dedoku Works

A Dedoku case starts with a building map. The map is divided into rooms, and each room can contain surfaces, blocked props, or ordinary floor squares. A witness can stand on normal floor squares and usable surfaces, such as a rug, chair, sofa, or bench. A witness cannot stand on blocked props, such as a shelf, painting, plant, display case, lamp, or other solid object.

Each case file gives a clue card for the witnesses, the missing item, and sometimes an anonymous tip. A clue might say that someone was in a specific room, in the same row as an object, beside a prop, alone in a room, north of another witness, or the only person on a certain surface. Some clues are direct, while others become useful only after you have narrowed down another witness.

The Main Rules

• One case piece per row. Once a witness or case item is placed in a row, no other case piece can use that row.
• One case piece per column. The same rule applies to columns, which is where the Sudoku-style logic comes in.
• Solid walls block beside clues. If a clue says someone was beside an object, the square must be directly north, south, east, or west of it, and a wall cannot sit between them.
• Direction clues use the grid. North, south, east, and west clues can point across rooms unless the clue specifically says the same room.
• People clues count people. If a clue says someone was alone or exactly two people were in a room, it is talking about witnesses, not the missing item, unless the clue names the item.
• The missing item is the final case piece. The case item is placed like the witnesses, but it represents what was found rather than another person.

Using Notes, X Marks, and Smart Mode

Dedoku is easiest when you treat it like a detective notebook. Add notes to squares that remain possible, mark impossible squares with X, and place a witness only when the evidence is strong enough. Smart mode is designed to keep that flow quick: tap to add a note, tap again to place a case piece, and use X mode when you want to rule out squares manually.

The hint button follows the same logic style. A hint might add possible squares for one clue, narrow existing notes, place a witness when only one square remains, or explain how a row, column, room, or anonymous tip affects the case. It is not meant to spoil the whole puzzle at once; it is meant to show the next useful deduction.

Difficulty Levels

Dedoku difficulty is not only about the size of the grid. Larger cases usually have more witnesses and a bigger map, but the clue set matters just as much. Easy cases use smaller grids and more direct clues. Medium cases add more object and room logic. Hard cases ask you to combine clues more often. Expert cases can include larger maps, anonymous tips, room counts, appearance traits, and clue chains where one deduction unlocks another.

The current difficulty ranges are built around that idea: Easy cases use smaller 6x6 to 8x8 maps, Medium cases use 7x7 to 9x9 maps, Hard cases reach 8x8 to 10x10, and Expert cases can go from 9x9 up to 12x12. The aim is to make each step feel richer, not just bigger.

Why Dedoku Is Family Friendly

Dedoku is inspired by the pleasure of solving a mystery, but it avoids a murder theme. The cases are about missing treasures, misplaced trophies, vanished keys, and other light detective stories. That makes it a good fit for players who enjoy mystery map puzzles, logic grid puzzles, escape-room style reasoning, or Sudoku variants, but want something with more character and setting.

Every puzzle asks the same satisfying question: what can you prove? If a clue only leaves two possible squares, mark both. If another clue removes one of them, place the witness. If an anonymous tip says exactly one person was in a room, use that as evidence against every arrangement that puts too many people there. The fun is not in guessing the hidden answer. The fun is in watching the case collapse, one careful deduction at a time.