Underwurlde: Routine at 57176

Used by the routine at Run_Game.

Lets a stalactite fall from the ceiling of a cave room every now and then. Nothing happens in a special room, in a room that has no ceiling, or while the stalactite record at Falling_Stalactite_Record is in use. The stalactite is only made when the low four bits of the tick counter and the frame counter, combined, are zero.

The record is a copy of the record of Sabreman, so the stalactite falls from the same x position, with the type 80 the y position 64 the attribute 70 (yellow) and a y velocity of 16 (see Handle_Falling_Stalactite).

Used by the routine at Run_Game. Lets a stalactite fall from the ceiling of a cave room every now and then. Nothing happens in a special room, in a room that has no ceiling, or while the stalactite record at Falling_Stalactite_Record is in use. The stalactite is only made when the low four bits of the tick counter and the frame counter, combined, are zero. The record is a copy of the record of Sabreman, so the stalactite falls from the same x position, with the type 80 the y position 64 the attribute 70 (yellow) and a y velocity of 16 (see Handle_Falling_Stalactite).
Spawn_Falling_Stalactite	57176	LD A,(IX+4)	Fetch the room y of the object.
	57179	CP 16	Return if it is a special room.
	57181	RET C	Return if it is a special room.
	57182	LD A,(43692)	Fetch the flags of the room that Sabreman is in.
	57185	AND %00000001	Keep only bit 0 (the ceiling).
	57187	RET Z	Return if the room has no ceiling.
	57188	LD A,(36666)	Fetch the type of the stalactite record.
	57191	AND A	Return if the record is already in use.
	57192	RET NZ	Return if the record is already in use.
	57193	LD A,(36566)	Fetch the tick counter and keep it in B.
	57196	LD B,A	Fetch the tick counter and keep it in B.
	57197	LD A,(23672)	Fetch the low byte of the frame counter.
	57200	OR B	Combine it with the tick counter.
	57201	AND %00001111	Keep only the low four bits.
	57203	RET NZ	Return unless they are zero.
	57204	LD HL,36634	Point HL at Sabreman_Record.
	57207	LD DE,36666	Point DE at Falling_Stalactite_Record.
	57210	LD BC,16	Set a counter of 16 bytes.
	57213	PUSH DE	Stash the address of the stalactite record.
	57214	LDIR	Copy the record of Sabreman to the stalactite record.
	57216	POP HL	Restore the address of the stalactite record to HL.
	57217	LD (HL),80	Set the type to 80.
	57219	INC HL	Move to the y position.
	57220	INC HL
	57221	INC HL
	57222	LD (HL),64	Set the y position to 64.
	57224	INC HL	Move to the attribute.
	57225	INC HL	Move to the attribute.
	57226	LD (HL),70	Set the attribute to 70 (yellow).
	57228	INC HL	Move to the y velocity.
	57229	INC HL
	57230	INC HL
	57231	INC HL
	57232	LD (HL),16	Set the y velocity to 16.
	57234	LD A,1	Set the redraw flags of the stalactite to 1 so that it is drawn without being erased first.
	57236	LD (36681),A
	57239	RET	Return.