Missing-digit & cryptarithm puzzles on a calm chalkboard. Just you and the board.
Free · No tracking · 300+ puzzles Coming soon to the App StoreRestore the hidden digits, or decode letters into numbers — verified solvable, exactly one answer each.
Recover the digits hidden inside + − × ÷ problems. From quick mental math to multi-step long division.
Each letter is one digit. Solve famous ones like SEND+MORE=MONEY and the legendary 1923 puzzle “The Solitary Seven.”
Deep chalkboard green, white chalk, nothing to distract you.
Every puzzle machine-checked for a single unique solution.
Hide the keypad and work things out right on the board with your finger.
Solve with no mistakes for ★★★. Streaks and an activity heatmap.
English, Japanese, Thai and Vietnamese — switch anytime.
No account, no login, no tracking. Progress stays on your device.
Play free. A single one-time purchase removes ads if you want.