Speedrun video games

Out-of-bounds glitches are rare in Doom but there's two places in E2M6 where that's fairly easy. Linedefs only count if the player's hitbox intersects them on a given tic. Normally you can't move quickly enough to do that.

IIRC you can wedge yourself into a diagonal corner (diagonal lines on the automap), find that wonky state where you're not moving but your gun still sways back and forth, and then mouse-strafe hard enough to eventually pop through into the void. If that sounds ridiculous, allow me to summarize: coding trig is hard.

This run uses an earlier diagonal corner and a rocket-boost instead. You'll notice the setup still requires the stuck-but-swaying thing. Incidentally this version was discovered by Alexo... on the GBA port. The framerate there is so wonky that OOB is feasible all over the place.

The real trick is ending the level. "Use" works kinda like hitscan and cannot cross a one-sided linedef. (I.e., a wall.) So you have to further abuse the game's slapdash collision detection by... uh... nudging the player through the wall? I think it works like picking up items through thin walls, where some work is done from your future position, before collision says you can't go there. In any case it was also somewhat recent, relative to thirty-ish years of people abusing this engine.

It's also possible to use the 'all ghosts bug' in e1m8 (haven't watched yet to see if it's used here - the runner may have judged it more time consuming to set up than it would save). A single projectile making too many collision checks can overwrite some memory and disable all collisions for the map. Then you're free to void walk to the exit. It's only useful on that one map because of its unique death exit that doesn't require a further collision check.