Sudoku Vault

Sudoku Vault comes in three board sizes: 4x4, 6x6 and the standard 9x9. Every size has its own four difficulty settings, named Basic, Normal, Hard and Expert, which gives twelve combinations to choose from before you place a single digit.

Two tools sit alongside the grid. Notes lets you pencil in the candidates you are still deciding between, so a cell can carry several small possibilities rather than one committed answer. Check is the other: press it and the game clears any wrong entries and locks the correct ones in place. That makes it a way to confirm progress partway through as well as at the end, and locked digits stay put afterwards.

The developer calls the design clean and the controls intuitive, and pitches the game as relaxing.

Pick a board size and a difficulty. Pick a cell with your mouse or touchpad and fill it by choosing a digit on the on-screen number pad. Turn on Note to add pencil marks instead of a final answer, and turn it off again to enter digits normally. Press Check whenever you want: wrong numbers are removed and right ones become locked.

Use Check as a midway test as well as a final one. Since it deletes mistakes and locks correct entries, a check after a run of guesses tells you exactly which cells to revisit. Keep pencil marks for cells with two or three options, and try a 4x4 board first if a 9x9 feels like a lot to start with.

A sudoku with three grid sizes and four difficulties for each. The frame is portrait. The developer lists a mouse or touchpad for selecting cells, with numbers entered from an on-screen pad, plus Note and Check buttons.

Sudoku for bro sticks to 9x9 but adds hints and an instant solve when you want to see the answer. Modern Sudoku drops the standard grid altogether for a board of 20 boxes.