Educational games have been around for ages—remember “The Oregon Trail,” the “Carmen Sandiego” games or “Math Blaster”? They were awesome, with dysentery and all that jazz. But nowadays, edutainment has become synonymous with the disembodied head of a Japanese doctor holding a degree in estimating how old your brain is. That’s great, but here’s the burning question: What does “Brain Age” teach me about sexually transmitted infections? Nothing. Allow me to guide your hands toward Zombie Cow Studios’ “Privates.” It’s not very hard or long, but hey, it’s free.

In “Privates,” you play as a squad of Marines wearing condom hats shooting at anthropomorphic STIs. Yup. Did I mention that it’s set inside a girl’s naughty bits? The opening level is called “The Way to Mount Vagina,” and the third is aptly named “Campaign in the Arse.” And in case you were wondering, yes, you can eventually lose your condom hat.

You only control the squad’s leader, so “Privates” ends up playing more or less like “Contra,” but instead of shooting nameless henchmen, you’ll be aiming four types of conveniently color-coded weapons at various STIs. Your spermicide blaster takes care of stray sperm, anti-viral clears out herpes, anti-fungal gets rid of yeast infections, and so on. There are some boss fights against particularly nasty infections spread throughout the game, but the experience isn’t going to break any new ground. Not that its lack of ambition is an issue—after all, you’re here to learn.

Like the rest of “Privates,” the educational portion is simplistic, relegated to pressing a single key whenever you come upon a previously unseen infection. It is, however, narrated by the most delightfully upbeat Englishwoman I’ve ever had the pleasure of listening to. Her descriptions of various STIs are genuinely helpful, giving a rundown of each infection’s symptoms, how it can be spread from “horny chump to horny chump,” and the means by which it can be treated, which also lets the player know which weapon to use.

If “Privates” sounds crude to you, it’s because it is, and it revels in its crudeness. Created by the same dynamic duo responsible for “Time Gentlemen, Please!”— in which Hitler wins World War II by way of Nazi dinosaurs—“Privates” has a sense of humor that is both sophomoric and brilliant. Take, for example, the game’s inspired interpretations of the human anatomy. The entrance to a girl’s vagina is blocked by a (cheap) toll booth, followed by a neat little escalator descending into its depths. Tacky neon signs that read, “CERVIX” and “G-SPOT?” illuminate the otherwise dark cavern. Another mission takes place on the surface of a man’s nether region, with short curly hair swaying in the breeze. I haven’t even mentioned the STIs yet, but let’s just say that the game’s interpretation of AIDS is as hilarious as it is politically incorrect, and let’s leave it at that.

The dialogue delivers just as many zings, and it’s fully voiced with cockney accents to boot. Your little squad of newbie recruits is responsible for some fantastic one-liners, including some spot-on “Left 4 Dead” references. When one of your recruits is attacked by a sperm, he shouts, “Get it off me! It’s making me pregnant!” The humor extends to other areas of the game as well—stumble upon a new type of STI and “Privates” pops up a message exclaiming “Flipping heck! You’ve unlocked an Attainment!” It’s enough to win anybody’s heart.

I seriously laughed more during my two hours with “Privates” than I have with any game I can remember. Even as I’m writing this, I can’t stop giggling like a schoolgirl. My only qualm is that it ends on a painful cliffhanger, but that will hopefully be remedied with the upcoming downloadable expansion set in the male genitalia next year, which Zombie Cow Studios describes as a “penis enlargement.” Classy.

Ending aside, trust me, you want to play “Privates.” It’s free and can be found at www.privatesgame.com. Download, laugh and learn.