3D Realms will always stand out in my mind for being the pack of mad bastards who turned the first-person shooter into a vehicle for the kind of self-consciously, incredibly politically incorrect comedy that was a big deal in the late '90s. Duke Nukem is basically what you'd get if you made a bunch of kids at the "hormone-filled sacks of fluid" stage of puberty create an action hero: he inhabits a world made entirely of mutated pigs in LAPD uniforms, strippers, and aliens that explode messily when shot with laughably enormous firearms.

The weird thing about playing Duke Nukem 3D now, of course, is how difficult it is. Duke seems like the kind of guy you'd put at the center of something like the Serious Sam games, where three dozen enemies are a light warm-up and a good stage is a broad, flat plain with two thousand aliens bearing down on you.

Naturally, though, this is a late nineties joint, made when Quake was a big deal, so Duke Nukem 3D plays like Doom with a number of extra elements bolted on and a juvenile sense of humor. It's genuinely difficult, rewarding twitch reflexes and persistence, and only the game's odd personality keeps you from feeling alone, claustrophobic, and outgunned.

The storyline's pretty much irrelevant, as you'd expect. Duke Nukem is a big hero, so when aliens attack Earth with intent to capture all the slender white women, he understandably objects. Starting in Los Angeles and moving up into space and beyond, Duke gets to shoot aliens, tip exotic dancers, fly around with his jetpack, and generally blow things up.

If you've played Doom, the game's episodic structure will seem immediately familiar, as will the general style of play. The game itself even knows where it's coming from on that; you can find a dead Doom Space Marine barely hidden in one of the first stages, in a small closet that's designed like part of Doom's version of Hell.

Duke Nukem is similarly challenging, with enemies able to take off large amounts of your health in one shot and resources being a bit scarce on the ground. It's a pure twitch-reflexes game, made to reward people who are able to acquire a target and blow it away in under a second.

What makes it oddly successful is that it manages to expand the limits of the FPS. Duke can actually pick up various items and use them at his discretion, such as scuba gear, protective boots, night-vision goggles, a jetpack, and a medical kit, allowing the player to use these items at his discretion instead of being forced to rely on whatever the level designer stashed nearby. This expanded the world tremendously, allowing Duke to fly and go underwater. 3D Realms was also smart enough to push the envelope with this, opening stages with huge vertical drops or large underwater sections.

At the same time, the game isn't afraid to start you off in a bad situation; the third stage begins with Duke in an electrical chair, so you're taking damage the moment the stage loads. There's a lot to admire here, and a lot that'd go on to inform other shooters. It's hard to imagine the genre's changed so much in such a short period of time, where twelve years ago, this was the state of the art.

Duke Nukem hasn't aged terrifically well, but the gameplay is very much still there. It's much more challenging than I remember it being, and a lot less funny, but it's a nice snapshot of first-person shooter history. You could do a lot worse with your Microsoft Points than to pick it up.