Robotron: 2084: Routine at E290

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 C42B; 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 34-37 a valid random screen position via Pick_Random_Spawn_Position_Y, and trailing bytes 0E 0D FF. Saves the updated entity list pointer to *Entity_List_Write_Pointer and writes the D1A4 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 C42B; 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 34-37 a valid random screen position via Pick_Random_Spawn_Position_Y, and trailing bytes 0E 0D FF. Saves the updated entity list pointer to Entity_List_Write_Pointer and writes the D1A4 list terminator.
Spawn_Horizontal_Wave_Enemies	E290	LD A,(HL)	Load the horizontal enemy count from *HL and store it at C42B.
	E291	LD ($C42B),A
	E294	INC HL	Return if the spawn count is zero.
	E295	AND A
	E296	RET Z
	E297	LD B,A	Set the spawn loop counter in B and stash the source pointer.
	E298	PUSH HL
	E299	LD HL,($C509)	Load the entity list write pointer from *Entity_List_Write_Pointer.
Spawn_Horizontal_Wave_Enemies_Record	E29C	LD DE,$CF52	Write the Step_Wide_Entity_Approach entity handler as a little-endian word.
	E29F	LD (HL),E
	E2A0	INC HL
	E2A1	LD (HL),D
	E2A2	INC HL	Advance past the handler word.
	E2A3	CALL Generate_Random_Byte	Generate a random byte via Generate_Random_Byte.
	E2A6	AND %00000011	Mask to the low 2 bits for the entity type offset.
	E2A8	ADD A,$34	Add 34 write the entity type, and advance.
	E2AA	LD (HL),A
	E2AB	INC HL
	E2AC	PUSH BC	Stash BC and call Pick_Random_Spawn_Position_Y to place the entity at a valid random screen position.
	E2AD	CALL Pick_Random_Spawn_Position_Y
	E2B0	POP BC
	E2B1	DEC HL	Restore BC and step back one byte.
	E2B2	LD (HL),$0E	Restore BC and step back one byte.
	E2B4	INC HL	Write trailing record bytes 0E 0D and FF.
	E2B5	LD (HL),$0D
	E2B7	INC HL
	E2B8	LD (HL),$FF
	E2BA	INC HL	Advance HL and loop back to Spawn_Horizontal_Wave_Enemies_Record for the next entity.
	E2BB	DJNZ Spawn_Horizontal_Wave_Enemies_Record
	E2BD	LD ($C509),HL	Save the updated entity list pointer to *Entity_List_Write_Pointer.
	E2C0	LD DE,$D1A4
	E2C3	LD (HL),E
	E2C4	INC HL
	E2C5	LD (HL),D	Write the list terminator D1A4 to *HL.
	E2C6	POP HL	Write the list terminator D1A4 to *HL.
	E2C7	RET	Return.