How to play
Fill every row, column and 3×3 block with digits 1–9 without repeats.
Notes are candidates you enter yourself. They do not place a final digit.
Show possibilities lists every digit currently allowed by the selected row, column and block.
H opens paid help for 8 coins. After confirmation it explains and performs one deterministic logical step, or points to the first wrong value if there is one. More help offers revealing a digit for 3 coins and filling notes for 2 coins in the selected cell. Undo does not refund coins.
Select a cell by touch or mouse, or move with the arrow keys. Use 1–9 to enter a digit, N for Notes, P for free possibilities and H for paid help.