Tap a cell to select it. The selected cell is highlighted. The rest of the board fades, leaving in full color the cells in the same row, column, or box, and in an X puzzle those on the same diagonal. The rest of the board fades, leaving in full color the cells in the same row, column, or group, and in an X puzzle those on the same diagonal. The rest of the board fades, leaving in full color the cells in the same row, column, or box (group, on an irregular board), and in an X puzzle those on the same diagonal. If the selected cell holds a digit, every other cell with that digit glows, making it easy to spot conflicts.
With no cell selected, tap a digit button to make every cell holding that digit glow; tap it again to stop. (Turning off Cell highlighting in Settings stops the glow.)
With a cell selected, tap a digit button (1–9) to enter your answer. The small number in the corner of each digit button counts how many more times that digit is needed. When all nine are on the board it shows 0, and the button dims.
To clear a cell, tap the same digit again (it toggles off).
Clue cells (bold digits provided by the puzzle) cannot be changed.