I just made the foundation for a game prototype, Hoarse, in Trabant:
It took me 30 minutes entirely without gameplay just to place the pieces and get them proportional in the right way. I'm probably on the wrong side of the advertised "prototype a 3D game idea in an hour," although not far off the mark I suspect.
My son's idea is to make an entirely ridiculous game about a horse that farts, barfs, bites and moves like a caricature of a stuffed animal. It just might work.
Ventures of an ex indie game developer