This is a normal Slitherlink.
Notes: Last week, I went to the 21st World Puzzle Championship as part of the unofficial U.S. B-team. I might write more about it later, but for now, I’ll just say that it was an awesome and inspiring experience and that it was great meeting so many people in person.
I haven’t constructed puzzles in a while, even though I definitely have the time to do so. There was a round at the WPC based on the number 21, so I figure that this puzzle will be good for getting started again.