Well, the most difficult part of Antichamber is that the 3D space is a non-euclidian one, so you have to adjust the way you think space. But I still think that the main game element is how to find your way from point A to point B in that space. And pathfinding isn't a trivial exercise in euclidian space, already, which is the point of the article.

I recommend the Talos Principle, even though I haven't finished it yet. Some challenges are quite hard, and it has even more spatial reasoning than portal. Here also, enigmas revolve around getting you from point A to point B, but you usually have to carry along some tools to help you. This often ends up being a variant of the Hanoi tower, or the wolf, goat and cabbage, but in a space with more than one dimension, unlike those classic riddles. And there is some lore hidden in the game world that can be quite interesting to puzzle together.

Now, if you want more portal, the game modding community is quite profusive around Valve's IP. You have Portal stories: Mel, Aperture tag, Portal: prelude. The quality is often worse than complete games, but the puzzles can be quite challenging.