This is a Slitherlink puzzle, with a twist. Every 3 in the puzzle is given to you. That is, if the solution has three segments around a single grid square, there is a 3 in that square.
I dare someone to make a normal slitherlink puzzle with this clue layout. Without doing something like adjacent 0s, I think it’s impossible. That should be the first sign these rules are a bit more interesting than they might appear to be at first. (At least, I was surprised.)
On that note, I apologize in advance for the fact that the solution is identical in some places on each side of the puzzle; the clue layout was a heavy constraint.