EVENT DAMAGEHPLANE
EVENT_DAMAGEHPLANE is a Game Event.
This event is triggered whenever a floor or ceiling is hit by a weapon. Note that kicks don't trigger this event nor does the radius damage of the devastator.
The number of the sector that was hit is stored in RETURN. When a floor is hit 131072 is added to RETURN and when a ceiling is hit 65536 is added to RETURN.
You can make pieces of glass fall down from the ceiling by setting RETURN to 1048576, this will also play the GLASS_BREAKING sound (this does not change the ceilingpicnum, you still have to do this yourself).