Guessed by @UnderwaterFunktown
This is almost like a glorified tech demo, what with how short of a game it is - it certainly feels like little more than a little test project compared to its sequel - but what a damn fine tech demo. It only goes on for a few hours but it's an unforgettable game for everyone who's played it. It's held one of the most stable positions in these rankings, and it'll probably continue to do so for as long as I'm doing them.