yotsu.

About yotsu.

yotsu., from the Japanese word for four, is built around a deliberately small daily ritual. Each day the app gives you a numbered set of four logic puzzles, and once you have solved them you are done until the next day. The developer, Florian Charnace, pitches it as something for the morning coffee or for winding down in the evening, without an endless feed pulling you back.

The four are classic pencil puzzles. Shikaku asks you to split the grid into rectangles, each holding one number equal to its area. Akari has you place lights so the whole grid is lit without two lights seeing each other. Binairo balances two symbols in every row and column under three simple rules. Sudoku is the familiar 9x9 grid. Each puzzle has one verified solution, and the puzzles open one after another through the day's set. Difficulty rises gently over time.

The app has no ads, no tracking and no account, and your progress, streak and stats stay on your phone. Yotsu Plus, a one-time purchase rather than a subscription, adds dark mode and themes, unlimited practice in any puzzle type and difficulty, and advanced statistics. It came out on the App Store in July 2026. It suits players who like Japanese-style logic puzzles and want a fixed, finite set each day.

How to play yotsu.

1. Open yotsu. to see the day's numbered set of four puzzles.
2. Solve the Shikaku: split the grid into rectangles, each with one number equal to its area.
3. Solve the Akari: place lights until every white cell is lit, with no two lights facing each other.
4. Solve the Binairo and then the Sudoku as they unlock.
5. Finish all four to keep your streak, and come back tomorrow.

Tips

• In Shikaku, start with the largest numbers in tight corners: they have the fewest possible rectangles.
• In Akari, numbered black cells next to walls often force lights; place those first.
• In Binairo, look for two equal symbols side by side: the cells on either side must be the other symbol.

Questions