The Door is a Portal entity that opens and closes on input. Never thought you'd see that, huh?
Doors are solid until they are triggered. Even though the door appears to simply move out of the way, the pieces are actually no longer solid.
- It actually uses two graphics, one for the center piece and the other for the main body, which is copied on the top and bottom.
- It looks like some weird hybrid between the doors from both Portal games.