In Dooms I and II, Lost Souls were originally intended to bounce elastically off floors and ceilings when they hit them.
Why it works Edit
Due to a coding error, the bouncing test was performed after the Lost Souls' momentum was set to 0.
In Ultimate Doom, Final Doom and Doom 95 this bug was fixed, causing many Doom II v1.9 demos to go out of sync.
- The great moderator at Doom Wiki for letting me use this info. Thanks! :)