On par with other Portal 2 fan games like Portal Stories: Mel. Some of the puzzles by the end felt either very simple, time consuming or taken directly from Portal or Portal 2 (especially the whole segment before the final big puzzle).

The new ideas it brings in are pretty interesting. I didn't expect the game to have fleshed out outdoor-like sections that feel really nice to not just be in boxy rooms all of the time. As well as bringing in new puzzle mechanics, I think it's really solid.

Other have noted the criticism of the ending, and without going into spoilers I felt there would be more. Once the credits rolls, I was there thinking "was that it?", like I expected a more fleshed out conclusion. It's hard to do when the game narratively takes place between Portal and Portal 2 and without wanting to disrupt the law like Portal Stories: Mel does.

As someone who likes puzzle games and a fair few Portal fan games over the year, it's definitely a highlight and considering that it's completely free is just the icing on the cake.