Antichamber is an insane FPS puzzle game that relies heavily on abstract puzzles based on shape and color and unreal structures that might completely change on you if you look away from them.
Pro Brilliant Puzzles
The primary theme to puzzles in Antichamber is that things aren't how they appear. If you walk down a hallway and turn around, you might be in a totally different area. This leads to some incredibly interesting and difficult puzzles, forcing you to think about the world around you in a totally new way.
Con Focuses less on its main selling point near middlegame
Near the middle of the game, you get a thing that a lot of the puzzles start to focus on, and the mind-bending puzzles and tricks to the player take more of a backseat as this mechanic changes the game to more of a traditional style of puzzle game. There are still elements of it, but much less of it.