DOOM Eternal has finally launched on PC, a day after many were able to pick it up from GameStop that have opted to willingly sacrifice their employees for physical copies of video games, and it feels great to step into the boots of the Marine and curb stomp the ever-loving Hell out of demons that are, fittingly, from Hell. Yet with the title comes two secret aspects that many aren't aware of; secrets that id Software themselves haven't spilled the beans on all of this time. \n \nYou'll need to find the old-school PC in the DOOM Installation, the central hub for your various butt-kicking escapades as the Marine. On the PC is Ultimate DOOM, the original hit DOOM with a new level added into it as an Episode IV: Thy Flesh Consumed. \n \nThe title itself is actually purchasable from Steam, although if you've picked up DOOM Eternal there's a bit of a surprise; you now own that game, inside of the game that you're currently playing, allowing you to play a game inside of a game that you're playing. Note that you'll need to collect all fourteen flop[py disks scattered about levels in order to access this. \n \nWait. No, that's right; a game inside of a game that is referencing itself. Doctor Emmett Brown, eat your heart out. \n \nhttps:\/\/twitter.com\/DOOM\/status\/1240971352020000770 \n \nThe second is a little bit trickier to access, as it simply shows a text field that you'll need to figure out what to enter in order to gain access. After much flailing about, the code has been figured out: 'flynntaggart'. \n \nIt's a reference to the only instance of the Marine actually being named in canonical lore, from four novels that began back in 1995. Granted, the primary protagonist was named Flynn Taggart, not necessarily the Marine himself. \n \nFlynn Taggart was a Corporal within the USMC that was responsible for the initial reaction to the invasion, although the novels began offering unique perspectives from a rotating cast of characters as the series went on. \n \nEntering the correct password will give you access to DOOM II, allowing you to play yet another full game within the full game that has two additional full games. The experience isn't even bad, all things considered; sure, you can scour the internet for some mods to make it a bit more playable on modern hardware, but the self-referential easter-egg has just solved a problem that computer scientists ask themselves every time they run into a new technology: 'Can it run DOOM?'