htmovflag has a nonzero value if the sprite is using a move command and it bumps into something (htmovflag is set to the return value of the movesprite function).
Depending if the moving sprite bumped into another sprite, wall, floor or ceiling, a different value will be added to the collided object's index:
(Compare with getzrange.)
- 16384 + sectnum, if a ceiling or floor was hit first
- 32768 + wallnum, if a wall was hit first
- 49152 + spritenum, if a sprite was hit first