The board is cut into regions of one to five cells. Fill every region with the digits from 1 up to the number of its cells, each once — a region of three holds 1, 2 and 3, a region of five the digits 1 to 5.

Two cells that touch — along a side or at a corner alone — never hold the same digit, whether or not they share a region.

Some digits come with the board.

Tap a cell and pick a digit on the pad under the board; the same digit again clears it. With notes on, digits are pencilled small in the cell instead. The digits the board came with stay put.

A reddish cell holds a digit its region already has or has no room for, or a digit touching its like.

Learn the solving techniques