Robotron: 2084: Routine at 58000

Used by the routine at Stage_Next_Wave.

Entry point called from Stage_Next_Wave. Reads the horizontal enemy spawn count from *HL and stores it at 50219; if zero, returns immediately. Otherwise loops B times, writing a full entity record into the entity list: the Step_Wide_Entity_Approach handler address, a random entity type in the range 52-55 a valid random screen position via Pick_Random_Spawn_Position_Y, and trailing bytes 14 13 255. Saves the updated entity list pointer to *Entity_List_Write_Pointer and writes the 53668 list terminator.

Used by the routine at Stage_Next_Wave. Entry point called from Stage_Next_Wave. Reads the horizontal enemy spawn count from HL and stores it at 50219; if zero, returns immediately. Otherwise loops B times, writing a full entity record into the entity list: the Step_Wide_Entity_Approach handler address, a random entity type in the range 52-55 a valid random screen position via Pick_Random_Spawn_Position_Y, and trailing bytes 14 13 255. Saves the updated entity list pointer to Entity_List_Write_Pointer and writes the 53668 list terminator.
Spawn_Horizontal_Wave_Enemies	58000	LD A,(HL)	Load the horizontal enemy count from *HL and store it at 50219.
	58001	LD (50219),A
	58004	INC HL	Return if the spawn count is zero.
	58005	AND A
	58006	RET Z
	58007	LD B,A	Set the spawn loop counter in B and stash the source pointer.
	58008	PUSH HL
	58009	LD HL,(50441)	Load the entity list write pointer from *Entity_List_Write_Pointer.
Spawn_Horizontal_Wave_Enemies_Record	58012	LD DE,53074	Write the Step_Wide_Entity_Approach entity handler as a little-endian word.
	58015	LD (HL),E
	58016	INC HL
	58017	LD (HL),D
	58018	INC HL	Advance past the handler word.
	58019	CALL Generate_Random_Byte	Generate a random byte via Generate_Random_Byte.
	58022	AND %00000011	Mask to the low 2 bits for the entity type offset.
	58024	ADD A,52	Add 52 write the entity type, and advance.
	58026	LD (HL),A
	58027	INC HL
	58028	PUSH BC	Stash BC and call Pick_Random_Spawn_Position_Y to place the entity at a valid random screen position.
	58029	CALL Pick_Random_Spawn_Position_Y
	58032	POP BC
	58033	DEC HL	Restore BC and step back one byte.
	58034	LD (HL),14	Restore BC and step back one byte.
	58036	INC HL	Write trailing record bytes 14 13 and 255.
	58037	LD (HL),13
	58039	INC HL
	58040	LD (HL),255
	58042	INC HL	Advance HL and loop back to Spawn_Horizontal_Wave_Enemies_Record for the next entity.
	58043	DJNZ Spawn_Horizontal_Wave_Enemies_Record
	58045	LD (50441),HL	Save the updated entity list pointer to *Entity_List_Write_Pointer.
	58048	LD DE,53668
	58051	LD (HL),E
	58052	INC HL
	58053	LD (HL),D	Write the list terminator 53668 to *HL.
	58054	POP HL	Write the list terminator 53668 to *HL.
	58055	RET	Return.