Thinking With Portals: Creating Valve's New IP

I love these making-of articles. Here’s one about Portal:

After we implemented the bare bones of getting a working portal system we had to figure out how to tackle some of the more complicated problems. For instance, how do you deal with one of our weighted cubes sitting halfway in a portal?

The player and other objects needed to be able to interact with both sides of the weighted cube and have that interaction be convincing. This also comes with interesting edge cases such as an object being able to actually collide with itself.

I can’t imagine how difficult (and rewarding) coding Portal must have been.