Fuck AI

See also: Portal Stories: Mel for some neat puzzles in the 60s aesthetic, and Thinking With Time Machine for a janky, frustrating mess with puzzles whose solutions you will spend almost as long repeatedly trying and failing to execute as you did coming up with them, but at least it has a cool aesthetic. (The movement replay gimmick is neat in theory. It's like co-op by yourself, except you have to do one half without being able to see what the other half is doing. You just have to trust that you get all the timing and the angles right.)

Oh, and P3TT (Portal 3 with Time Travel), a fanmade Unity game that contains perhaps my favorite implementation of time travel of the three. Shoot your green portal once to record and put stuff in it. Shoot it again to play the recording back. Everything that went in (lasers, cubes, etc) will come back out at the same times they went in. It also has outstanding puzzles.