id Software’s 2D platformers outperformed early FPS titles by “10 times” in revenue, raising questions about the future of Doom had the studio chosen the easier path.

Doom and Wolfenstein 3D might not have come to life if a developer hadn’t nearly toppled out of his chair while playing the underperforming FPS, Catacomb 3-D.

While Wolfenstein 3D is often hailed as the starting point for modern FPS games, paving the way for Doom to elevate the genre to new heights, neither title was id Software’s first foray into first-person shooters. That honor goes to Hovertank 3D, the studio’s initial venture, while Catacomb 3-D marked their first attempt at a character-driven FPS.

Despite the groundbreaking impact of Wolfenstein and Doom, their existence was almost jeopardized by id’s financial missteps. The studio only raked in $5,000 from Catacomb 3-D—about “ten times” less than what their 2D platformer series, Commander Keen, was earning. Fortunately, a moment of surprise changed everything.

John Carmack reminisced about a memorable incident during the development of Catacomb, where Adrian Carmack nearly fell out of his seat upon encountering a troll. “This is where we could tell we’re starting to get it,” John explained, noting that this moment signified a shift in gaming. “This was the future of gaming, rather than just watching little sprites move around. It was the shock factor that made me realize we were onto something big in this new genre.”

Adrian defended the game’s immersive visuals, stating, “It just automatically sucked you in. You couldn’t help it. That was one of the craziest things in a video game I’d ever seen. We definitely knew we had discovered a new game style.”

Even though Catacomb didn’t achieve massive success, Romero recalls a pivotal conversation one night where they recognized Catacomb 3-D as the dawn of a new gaming experience, leading them to decide on their next project: Wolfenstein 3D, the progenitor of first-person shooters.