The game is called CLOP, and it’s a simple premise; guide a unicorn across a field to the fair maiden. The problem is that unicorns have four legs, and every movement of every leg is up to you. Oh, and once you’ve mastered that trick, the hill appears and murders your world. Check out this article on CLOP and how it’s designed to grief its players. On purpose, because that’s where the fun is. Gamasutra has the story.