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.