Every puzzle has exactly one solution solvable by pure logic. No guessing, no trial and error. If stuck, there is a deduction you have not found yet.

Press and hold the Reset button for about half a second. A confirmation will appear to prevent accidental resets.

Use two fingers to scroll the grid when zoomed. Single finger selects cells. Pinch to zoom in and out.

Press and hold the button for half a second. It fills every empty cell with all valid candidates based on current board state — cage sum rules included. No advanced logic applied.

Tap Pencil to enter note mode. Select a cell, then tap digits to add or remove candidates. A dot appears under numpad digits already noted in the selected cell. Double-tap a single note to place it as your answer.

Expert requires Rule of 45 and cage combinations. Master requires locked combinations. Extreme requires cross-cage interaction chains. Each tier is certified — only those techniques are needed.

Hold a numpad digit for half a second to lock candidates — all other candidate numbers dim across the board. Hold again or tap a cell to release. Useful for tracking a digit across the whole grid.