In-Out Slitherlink Description

In-Out Slitherlink is a variation of Slitherlink. Clues appearing inside the solution loop are correct. Clues appearing outside are inverted; they instead tell the number of segments not drawn around the square minus one. So a 0 that is outside the loop has only one undrawn segment around it, meaning it functions as though it were a 3 in standard Slitherlink. It is up to the solver to determine which clues are correct and which are inverted. The solution is unique.

Below is an example puzzle and its only solution. The inside of the loop is shaded in the solution.