How to play

Every row and every column has a target sum, shown at the end of the line. The board starts with every number in play. Cut numbers out until each row and each column keeps exactly its target.

1. Tap a number to cut it; tap it again to put it back.
2. Read the line — a target turns green when the line is exact, and warms up while the line still adds to too much.
3. Undo steps back one cut, Hint fixes one cell from the stored answer and counts itself, Restart puts every number back.
4. Win — all rows and all columns match their targets. Each board was checked to have exactly one answer.

Targets are plain sums, so a row target of 20 can be four 5s, a 9 and an 11, or a dozen other combinations — the columns are what pin it down. Add ?puzzle=7 or ?level=hard to the address to pin a board.