It has been 20 years since Wolfenstein 3-D changed the course of “shoot’em up” games forever.

For those of us who remember getting jumpy in front of our PC computers, the 1992 precursor to Doom and many other games since is a first-person shooter classic. And to celebrate two decades since its inception, Bethesda Softworks, the company that now owns the property, has released a browser-based version of the game.

One of the first to present a true “3-D” view for the player, id Software’s Wolfenstein 3-D pitted a captured American spy against that most expendable of enemies, the pixilated German Nazi soldier. The game’s moving walls and secret passageways came to life in visceral ways that earlier birds-eye view-style shooting games didn’t, and helped establish a kind of game play perspective that has been used ever since.

So while Call of Duty and others are far more realistic, don’t be surprised to see some desktops showing Wolfenstein’s sharp corners this week—it’s the game that launched a thousand shooters.