The basis for Organ Trail is identical to its educational counterpart -- you'll need to search out food, repair your vehicle and make it across the country. There are, of course, some noticeable differences: having zombies attacking you throughout, having to fjord a mass of zombies instead of the Mississippi, shooting zombies instead of buffalo; you get the point. It might actually be more educational than the original. At least you're not bringing extinction on a whole species -- or if you are, they're a really mean species.
While you're traveling the post-apocalyptic DC wasteland, you'll see plenty of nods to other games, not just Oregon Trail (although, make sure you check out the tombstones along your way). There are bits and pieces of video game references throughout the experience, from Resident Evil to Left 4 Dead.
Organ Trail comes from The Men Who Wear Many Hats, who seem to have a penchant for releasing completely absurd Flash games. If you don't believe us, check out Blind Samurai. Even their description of Organ Trail is tongue-in-cheek, "Relive your childhood with this faithfully emulated version of Organ Trail for the Apple-II."
Halloween might be come and gone, but zombies, as they say, are forever. At least until you shoot them with your shotgun. Play the game here.