'Doom' player uncovers a secret that's been hidden for 24 years

Video games are often filled with secrets. They just don't usually stay hidden for this long.

Doom series co-creator John Romero took to Twitter on Friday with an exuberant congratulations for Zero Master, the YouTuber who discovered a secret unlock that's confounded Doom II fans for more than two decades. The secret is out now, and Romero is thrilled.

"CONGRATS, Zero Master! Finally, after 24 years! 'To win the game you must get 100% on level 15 by John Romero.' Great trick getting to that secret!" Romero wrote, before going on to explain how the trick works.

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To be clear, the location itself isn't the secret here. Doom and its sequel have been a source of public fascination for decades, and dedicated programming-savvy fans discovered all of its hidden areas long ago.

What's unique about this one, however, is no one's ever managed to unlock it without cheating. As such, no one has ever been able to claim a 100 percent completion -- a milestone that requires players to find every secret in the game -- in the 24 years since Doom II launched. Until now.

As Romero pointed out, the teleporter leading to the area doesn't work if you step onto it yourself; it can only be triggered when an enemy knocks the player into it. Looking at the description on the YouTube clip, it seems that even Zero Master wasn't clear on how the unlock happened.

"While the secret location has always been known, it has been considered impossible to trigger it and thus get 100% secrets in the intermission screen," the description reads.

Then, later: "This trick has something to do with the moving door and the pain elemental spawning a lost soul on top of you. This forces you down to the lowest floor the moving door is on, which puts you within the secret sector and on the same height, thus triggering the secret."

Full game completion is a big deal among dedicated fans, so this is a huge development for the Doom-loving community. It's now finally possible to truly, fully beat the game, secrets and all. Congrats, Zero Master. And congrats to Romero as well for not having to hang onto that secret any longer.