Underwurlde: Routine at DF58

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 50 the y position 40 the attribute 46 (yellow) and a y velocity of 10 (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 50 the y position 40 the attribute 46 (yellow) and a y velocity of 10 (see Handle_Falling_Stalactite).
Spawn_Falling_Stalactite	DF58	LD A,(IX+$04)	Fetch the room y of the object.
	DF5B	CP $10	Return if it is a special room.
	DF5D	RET C	Return if it is a special room.
	DF5E	LD A,($AAAC)	Fetch the flags of the room that Sabreman is in.
	DF61	AND %00000001	Keep only bit 0 (the ceiling).
	DF63	RET Z	Return if the room has no ceiling.
	DF64	LD A,($8F3A)	Fetch the type of the stalactite record.
	DF67	AND A	Return if the record is already in use.
	DF68	RET NZ	Return if the record is already in use.
	DF69	LD A,($8ED6)	Fetch the tick counter and keep it in B.
	DF6C	LD B,A	Fetch the tick counter and keep it in B.
	DF6D	LD A,($5C78)	Fetch the low byte of the frame counter.
	DF70	OR B	Combine it with the tick counter.
	DF71	AND %00001111	Keep only the low four bits.
	DF73	RET NZ	Return unless they are zero.
	DF74	LD HL,$8F1A	Point HL at Sabreman_Record.
	DF77	LD DE,$8F3A	Point DE at Falling_Stalactite_Record.
	DF7A	LD BC,$0010	Set a counter of 10 bytes.
	DF7D	PUSH DE	Stash the address of the stalactite record.
	DF7E	LDIR	Copy the record of Sabreman to the stalactite record.
	DF80	POP HL	Restore the address of the stalactite record to HL.
	DF81	LD (HL),$50	Set the type to 50.
	DF83	INC HL	Move to the y position.
	DF84	INC HL
	DF85	INC HL
	DF86	LD (HL),$40	Set the y position to 40.
	DF88	INC HL	Move to the attribute.
	DF89	INC HL	Move to the attribute.
	DF8A	LD (HL),$46	Set the attribute to 46 (yellow).
	DF8C	INC HL	Move to the y velocity.
	DF8D	INC HL
	DF8E	INC HL
	DF8F	INC HL
	DF90	LD (HL),$10	Set the y velocity to 10.
	DF92	LD A,$01	Set the redraw flags of the stalactite to 01 so that it is drawn without being erased first.
	DF94	LD ($8F49),A
	DF97	RET	Return.