Trace Numbers consists of a rectangular or square grid with numbers in some cells. The aim is to draw as many lines into the grid as it contains cells with the number 1. The line may only travel horizontally or vertically, and never diagonally. The line starts in the cell with the number 1 and visits all cells with numbers in order through the highest number. Each cell must be visited exactly once; lines cannot cross.
Cross+A can solve puzzles from 3 x 3 to 30 x 30.