As many will no doubt be very aware, Doom Eternal is far from the first game in the demon-slaying franchise. In reality, Doom is actually one of the most defining video game properties in the history of the medium, with many of the series’ earliest entries doing a lot to innovate the shooting genre and cultivate it to the level it’s at today. It seems the creators of Doom Eternal have a lot of reverence for the series’ groundbreaking origins, as can be seen in two incredible easter eggs that can be accessed within the game’s hub, the Fortress of Doom.

As it turns out, there are actually two classic Doom games inside of Doom Eternal, with players being able to gain access to both through some fairly hard to discover means. These games are both the original Doom and its sequel, Doom 2: Hell on Earth, with each being playable on the Doom Slayer’s computer in the Fortress of Doom after certain parameters have been met.

Unlocking the original Doom is the hardest to achieve of the two. Players must scour the whole campaign for the 14 floppy disc collectibles that lie in wait in nearly every level of the game. By extension, the player will have had to have beaten the game to be able to play the original Doom, which will only become unlockable when all the floppy discs have been collected. Of course, the original game is a classic, and it’s fantastic to think that players will be able to experience the retro title through this incredible easter egg.

Doom 2: Hell on Earth, on the other hand, is much easier to find. The player simply has to go to the Doom Slayer’s room and interact with his old computer. Here, they’ll be met with two squares filled with floppy discs with question marks beneath them, to which they select the one on the right and input “FLYNNTAGGART.” Hell on Earth will then appear on the computer, allowing the player to load it up and enjoy the classic Doom sequel. With the second Doom title so closely mimicking the plot of Eternal, it seems fitting that players will get to experience it through the long-awaited next entry in the series.

Of course, fans likely won’t be too preoccupied with playing these two games when Doom Eternal has so much to offer. With a campaign that stretches over roughly 16 hours and a ton of side content that supposedly elongates that runtime dramatically, it’s clear Eternal offers tons of explosive Doom action, being labeled by many as one of the best entry in the series.

Doom Eternal is available now on PC, PS4, Stadia, and Xbox One, with a Switch version currently in development.