Here’s something you can add to the list of things you never knew existed, but could probably definitely use: it’s called the “Evolution Door,” which is a “flip panel” invention by Austrian designer Klemens Torggler.
Torggler actually has more than one alternative to the classic door concept that’s been around for centuries. They all utilize rotating squares, but some use rods, wheels and a track system arranged in an epitrochoid curve.
According to io9:
The Evolution Door works by virtue of four strategically attached triangles that separate, fold and rotate with a gentle flick of the wrist. It’s a wonderful play on geometry that makes it possible to move the screen from side to side without the use of a track, a topological trick that Torggler says “opens up new applications for the door.”