How to play Deduce
Four people, three things to work out about each, and a set of clues that only ever rule things out. It is the shelf’s sit-down puzzle: a good solve takes a few minutes, beating seven earns a bonus, and stepping away pauses the clock and keeps your grid.
The rules
- Four people, and three categories to work out for each one. Every value is used exactly once down a column — if Ben has the parrot, nobody else does.
- Each cell starts holding every possibility. Tap one to cross it off. When a single possibility is left, that cell is settled.
- Tap a clue to gray it out once you have used it. That is your own bookkeeping — it has no effect on the grid. A grayed clue folds away at the top of the list, so the ones you still need stay next to the grid. The clues open at full length; the button in the box's corner fits them to the screen so they scroll and the grid stays put. Tap the “clues used” line to open them, and tap a grayed clue to bring it back.
- Fill every cell, then press Check. You get three checks; run out and the answer is shown — green where you had it, red where you didn’t — and you keep credit for the cells you had right.
- Undo steps back through your crossings-off. Reset clears the grid, your notes and any hint clues, and gives the three hints back — it asks before it does it.
- Leave the page and the clock stops. It restarts when you press Continue, not when you come back.
You never have to guess
This is the promise the game is built around, and it is checked rather than hoped for. Before a grid ever ships, a solver proves two things about it: that exactly one arrangement satisfies the clues, and that it can be reached by crossing off alone — no point where the only way forward is to try something and see.
So if you are stuck, there is something in the clues you have not used yet. That is a much better place to be than wondering whether the puzzle is fair.
How to read the clues
- A negative clue is a single cross. "The Foxes runner is not the one in 4th" removes one possibility and nothing else. Do it and move on.
- A positive clue crosses off four things, not one. "Eve is the parrot owner" settles Eve's pet — but it also means nobody else has the parrot, and Eve has none of the other pets. New players take the one cross and leave the other four on the table, and that is the single biggest source of being stuck.
- Relational clues constrain both ends. "Exactly two places after Vic" tells you where Vic cannot be as much as where the other person can. If there are four positions, Vic cannot be in the last two.
- One column is ordered, and it reads as a list rather than as a picture. It runs top to bottom in ascending order, so floor 3 is printed above floor 6 and 1st is printed above 6th. "A lower floor", "earlier" and "ahead of" therefore mean further up that column, and "two floors after" means further down it. Reading the column as a drawing of the building — top of the list, top of the block — inverts the whole axis and makes the clues look as though they contradict each other.
- Watch for the last one standing. If three people cannot own the banjo, the fourth does — even if no clue ever mentions them. Scanning each row and column for a value with only one home left is where the endgame usually is.
Hints
A hint gives you another clue, never an answer. You still have to apply it. There are three per puzzle and they are counted, not punished — each costs eight points, which is a fair trade for finishing a grid that had you beaten.
If you had ruled out something a new clue says is true, taking the hint puts it back.
Scoring
Solving costs you nothing beyond the checks you spend: 90 on the first check, 80 on the second, 70 on the third. Finishing inside seven minutes adds 10, taking over twelve loses 10, and each hint is −8. A spent grid still scores for the cells you had right.
Full details on how scoring works.