John Romero tweeted today that he made his first Doom level in 21 years.

The co-creator of the landmark game included the level on a Dropbox link. Doom first debuted 22 years ago as one of the seminal titles that cemented the first-person shooter genre that has become a multibillion-dollar business. Id Software, and later its new owner Bethesda, created a whole series of games based on the Doom brand.

Romero was one of the original band of creators of Doom, along with John Carmack and Tom Hall. Romero is no longer working on the series, but Bethesda has a version with high-end, modern-day 3D graphics coming out sometime in 2016. I interviewed Romero back in 2013 at an event for the 20th anniversary of Doom. He was still a wiz at playing the game, and he was clearly very proud of the creation, which introduced the idea of the “deathmatch” that is a staple in shooter games today.

I emailed Romero today about why he did this. He wrote back, “Whenever I start a new game, I usually warm up, so to speak, by creating levels in something I’m familiar with. That way, the focus is on the creation and not the tools. In this case, I decided to start out with DOOM as the levels are relatively easy to create, especially with today’s modern tools. I used DoomBuilder, and it was just a total delight to use. I absolutely loved making a level using it.”

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He added, “As for the level, E1M8 was an obvious choice for me. Out of the shareware episode of DOOM, E1M8, the boss level, was the only level I didn’t make. Sandy Petersen did an amazing job with the original one with the very memorable Barons of Hell right in your face at the end, of course.”

Romero said he restricted himself to the DOOM1.WAD, which includes the shareware-only assets.

“So the level is made with the same restrictions it would have had back in 1993,” he said.

Asked what the legacy of Doom was, Romero said in 2013, “Geez. The first-person shooter genre. Video game violence. Multiplayer. Maybe e-sports. The game engine. Modifying games. The mod community, which is where Portal and Team Fortress and Counter-Strike and all these other huge franchises came from.”