Robot Lines: level 1

Normal sudoku 4x4 rules apply.

Each line contains an inspection robot, which moves backwards and forwards along it. The starting position must be deduced. The robot inspects this starting digit, which tells it how many cells along its line it must move. It can move in either direction, as long as there is enough room for it to move the correct distance without going off an end of the line (it can't reverse direction mid-movement.)

The robot then inspects the digit it stops at, which again tells it how many cells to move, again in either direction. The robot must repeat this process, each time obeying the digit it stops at, until it has inspected EVERY cell along the line. (It can ignore the last digit it inspects, and stops there.)

The robot must never stop at the same cell more than once. Digits may repeat on lines if allowed by sudoku.