Twenty years ago, a game came out that paved the way for a whole generation of titles. Before the Modern Warfare games, before Master Chief took on the aliens in Halo, and before puzzles took on the first person view in Portal, there was this.

In 1992, a small group of developers created a game called “Wolfenstein 3D”. While not technically the first game to push the first-person shooter genre, Wolfenstein is often seen as the first to really make its mark.

For its twenty-year anniversary, Bethesda – the current owners of the company that made the game – has made the iPad, iPod Touch, and iPhone version free.

Wolfenstein 3D normally costs $1.99 on the AppStore, so make sure you grab it today.

And if you don’t have an iOS device, you can always head online and play the game in a web browser at Bethesda’s Wolfenstein page.

Parents take note that there is a bit of blood and themes of Nazi killing in the game, though thanks to how old the title is, these are by no means realistic.