What a great app that was. The step-by-step animated folding instructions were actually 3D. It had buttons to rotate the view around to any angle. In hindsight they must have written their own simple 3D engine or something. Obviously they didn't need to render too many polygons at once, and no textures or shading.
The thing I'm most impressed and surprised about is that archive.org runs a Windows 3.1 emulator in the page, so you can actually use the program. I fully expected it to just be information about the program, perhaps with some screenshots. Modern browser tech is amazing.