Draw a line that starts at 0 and visits numbers 0 to 9 in order. The line can only be horizontal or vertical, cannot cross itself, and can only change direction at dots. All dots must be visited.

. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . 2 .
. . . 9 . . 0 . . .
. . . . . . . . . .
. . . . 5 . 7 . . .
. . 6 . . 8 . . . .
. 1 . . . . . . . .
. 3 . . . . . . . 4
. . . . . . . . . .