If you grew up in the '90s, you'll have seen people staring cross-eyed into Magic Eye books at some point, books about visual illusions contained inside 2D images.
Now imagine DOOM, but as a constant, moving Magic Eye image.
"OMDO plays just like DOOM, except every frame is a random dot autostereogram," the itch.io page for the mod reads. Random dot autostereograms, incidentally, are the same ones that the Magic Eye were based on.
OMDO basically transforms the first three levels of DOOM into a giant, moving Magic Eye image. It's only the first three levels because that's what is available as shareware. Given that the game is opensource, however, someone should be able to use the autostereogram algorithm to convert everything.
Some much needed advice.
Mind you, I'd venture that too many people wouldn't be able to tolerate this for too long:
To drive yourself insane, and for a neat DOOM-themed distraction, head here.