Smart Sudoku starts on a board of nine cells. You place digits by reading clues rather than by guessing: a green clue means the digit stands only in the marked cells, a red one means it cannot stand there. A move that breaks a clue simply does not happen, so there are no lives and no penalties.
Once the idea clicks, three classic modes open up on a 9×9 board: classic sudoku, jigsaw sudoku with irregular regions and killer sudoku with caged sums.
There are 2750 checked puzzles inside, five difficulty levels in every mode. When the catalogue runs out, the game keeps building new puzzles on its own, and each of them has exactly one solution.
Hints explain a move in three steps: where to look, why it follows and the answer itself. There is a daily goal, 32 achievements, six leaderboards and 16 themes. Progress saves itself and follows you between devices.
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How to play
A move takes two taps: pick a digit on the bottom panel and then a cell on the board, or the other way round. You can also drag a digit with a finger or the mouse: from the panel into a cell, from one cell to another, or off the board to erase it. Tapping a filled cell takes the digit back.
On a computer the number keys, the arrow keys, Z for undo and N for notes all work.
The game runs in any phone orientation, so there is no need to turn the device. A puzzle is solved when every digit sits by the rules of its mode. There is no timer and no lives: a wrong move is refused, and the game says which clue stopped it.
The hint button gives three levels of explanation and the first two are free. Progress saves automatically after every move, and no sign-in is required.