It creates puzzles with multiple possible solutions:
5 6 3 _
4 _ _ _
6 7 4 _
_ 4 _ _
The bottom right corner can be in the loop, or out of the loop, and both solutions are valid.
5 6 3 _
4 _ _ _
6 7 4 _
_ 4 _ _
The bottom right corner can be in the loop, or out of the loop, and both solutions are valid.