Expect work productivity to drop today. Wolfenstein 3D is being released as a free in-browser game by Bethesda Software to mark the 20th anniversary of the game's release.

Wolfenstein 3D, which can be played here, is considered one of the earliest first-person shooters, and the game that made the genre popular on PC. It was developed by John Carmack at id Software and published by Apogee Software in 1992. The game originally was released for free as shareware, but then was later released as a paid PC game and on several consoles.

The browser version is the full release of Wolfenstein 3D; you play an American soldier in WWII attempting to escape from the Nazi stronghold of Castle Wolfenstein. You must navigate the 3D maze while fending off Nazi soldiers, attack dogs and mutant monsters.

Wolfenstein 3D was not the only stop for Carmack and designer John Romero; the duo later developed DOOM, the mega-popular 1993 FPS that was downloaded by 10 million people in the first two years.

Bethesda Software also announced they would be dropping the price of the iOS version of Wolfenstein 3D (iTunes link) to commemorate the anniversary. For a limited time, gamers will be able to pick up the classic for free on their iPhone, iPod touch, and iPad on Wednesday..

Are you excited about the rerelease of Wolfenstein 3D? Do you have fond memories playing the title when it came out 20 years ago? Let us know in the comments.

BONUS: Classic Games to Play Online

Below, check out our list of official remakes, ports and offers of classic video games that found new life on social platforms and free sites.