A brain teaser where everything can be proved
123doku is a logic puzzle game for mobile, free and playable offline. One grid, stones of weight 1, 2 or 3, and two constraints: the total each row and each column must reach, and the rule that two stones of equal weight may never touch side by side.
It belongs to the family of pure logic puzzles — the one that holds sudoku, kakuro and takuzu — without borrowing a single one of their rules. What it does take from them is a promise: one solution, and never a square you have to guess.
The rule, in three sentences
Every cell takes a stone of weight 1, 2 or 3. Each row and each column shows the weight it must reach, and two stones of the same weight can never touch side by side — diagonally, it is allowed.
Only one arrangement is possible, and all of it is provable: no cell is ever guessed. When you get stuck, the game shows where to look and which rule applies — never the answer.
How to play
A game comes down to a few moves:
- Tap a cell, then pick the stone — 1, 2 or 3 — to drop on it.
- Compare the row and column totals with the target weights, shown on the right and underneath.
- Check that no stone touches another of the same weight side by side. Diagonally, they may sit next to each other.
- Pencil in the weights still possible in a cell while more than one holds.
- Ask for a hint when you are stuck: the game points at the cell to look at and the rule that settles it, never its value.
- The puzzle is done when every row and every column reaches its weight.
Nothing has to be learned first, and no arithmetic is needed beyond adding a handful of small numbers.
How it differs from sudoku
- In sudoku you place the digits 1 to 9 and never repeat one inside a row, a column or a box. In 123doku the weights repeat as often as they need to: what is constrained is their total, not their uniqueness.
- Kakuro also asks for sums, but with all digits different inside each run. 123doku only asks for one total per row and per column; its single prohibition is contact between two stones of the same weight.
- Takuzu, also known as binairo, fills its grid with two values; 123doku uses three. As in all three games — and this is the family resemblance — nothing is guessed: every cell can be proved.
What it looks like
What is inside
- Over 140,000 puzzles, from 5×5 to 8×8.
- A difficulty that adjusts as you progress.
- A daily puzzle, the same one for everybody.
- A daily league and a ranking that resets every day.
- Duels: challenge a friend on the same grid, against the clock.
- Coins that are not for sale: you earn them, you never pay for them.
- Offline: the puzzles are installed with the game.
- Six languages and six themes.
- No account: no address, no password, no sign-up.
Frequently asked questions
What is 123doku?
123doku is a logic puzzle game for mobile. You drop stones of weight 1, 2 or 3 onto a grid so that every row and every column reaches exactly the total shown, and so that two stones of the same weight never touch side by side. Every puzzle has a single solution, and all of it can be reached by reasoning.
Is 123doku a sudoku?
No. 123doku takes its inspiration from logic puzzles such as sudoku, kakuro and takuzu, but it borrows none of their rules. You do not place digits that must all differ: you adjust weights until each row and each column reaches its total, and the same weights may repeat as long as they do not touch.
How do you play 123doku?
You tap a cell and drop a stone of weight 1, 2 or 3 on it. The game shows the target weight to the right of every row and below every column, along with the total already placed. You progress by ruling out impossible weights cell by cell; a pencil lets you note the remaining options, and a hint shows where to look when you are stuck.
Is 123doku free?
Yes, 123doku is free. The game is funded by advertising and has no in-app purchases: coins are used to ask for hints, they are earned by playing, and they are not for sale.
Can you play 123doku offline?
Yes. The puzzles are installed with the game, so everything plays offline — on a train, on a plane, away from any signal. A connection is only needed for the daily league and for duels with friends, which catch up as soon as one comes back.
Do you need an account to play?
No. 123doku asks for no email address, no password and no sign-up. Your progress is attached to a randomly generated identifier, and a recovery code lets you find it again on another phone.
What devices does 123doku run on?
123doku is an Android mobile game. There is no iPhone version at the moment.
Where to get it
Coming soon to Google Play
123doku is coming to Android. The Google Play listing will be announced here.