Cursectnum

This is the sector that the player is in. This generally shouldn't be altered unless you're doing something such as teleporting the player. Unlike a sprite's sectnum value, this value is not stored in or part of a linked list and may equal -1 if the player is currently outside of a sector.

A player may go outside of a sector by being crushed in a swinging door, using glitches and bugs to accelerate themselves fast enough to pass through walls (and into null space) or by simply using the "no clipping" cheat code.