Robotron: 2084: Routine at CF52

CF52: Step Wide Entity Approach

Per-entity frame handler for an approaching wide entity. Advances the scroll counter, moves the entity down by eight pixels per frame, and on the final frame installs Handle_Horizontal_Enemy_Entity as the entity's new handler. Called from Main_Game_Loop.
Step_Wide_Entity_Approach	CF52	EX DE,HL	Copy the entity pointer to DE.
	CF53	LD HL,($C535)	Advance the animation phase counter by 40.
	CF56	LD BC,$0040
	CF59	ADD HL,BC
	CF5A	LD ($C535),HL
	CF5D	EX DE,HL	Copy the entity pointer back to HL.
	CF5E	LD A,D	Jump to Step_Wide_Entity_Approach_Wrap to wrap the approach at the screen boundary.
	CF5F	CP $0F
	CF61	JR Z,Step_Wide_Entity_Approach_Wrap
	CF63	JR NC,Step_Wide_Entity_Approach_Advance_Six	Jump to Step_Wide_Entity_Approach_Advance_Six if the entity's approach descent is complete.
	CF65	EXX	Load the entity draw colour.
	CF66	LD B,A
	CF67	INC B
	CF68	EXX
	CF69	PUSH HL	Draw the entity sprite.
	CF6A	CALL Draw_Wide_Entity_Sprite_Pixels_Only
	CF6D	POP HL
	CF6E	INC HL	Move the entity eight pixels down the screen.
	CF6F	LD A,(HL)
	CF70	ADD A,$08
	CF72	LD (HL),A
	CF73	DEC HL	Step back within the entity record.
	CF74	LD A,($C536)	Skip spawning if this is not the final approach frame.
	CF77	CP $01
	CF79	JR NZ,Step_Wide_Entity_Approach_Draw
	CF7B	EXX	Switch to the entity arrival colour INK: GREEN, PAPER: BLACK (BRIGHT) .
	CF7C	LD B,$44
	CF7E	EXX
	CF7F	PUSH HL	Draw the entity's arrival frame.
	CF80	CALL Draw_Wide_Entity_Sprite
	CF83	POP HL
	CF84	DEC HL	Install Handle_Horizontal_Enemy_Entity as the entity handler to begin horizontal movement.
	CF85	LD DE,$E1B6
	CF88	LD (HL),D
	CF89	DEC HL
	CF8A	LD (HL),E
	CF8B	LD DE,$0008	Advance eight bytes to the next entity record.
	CF8E	JR Step_Wide_Entity_Approach_Advance	Advance eight bytes to the next entity record.
Step_Wide_Entity_Approach_Wrap	CF90	INC HL	Reset the descent position to wrap the approach path.
	CF91	LD A,(HL)
	CF92	SUB $70
	CF94	LD (HL),A
	CF95	DEC HL	Step back and prepare the draw colour.
	CF96	LD A,D	Step back and prepare the draw colour.
Step_Wide_Entity_Approach_Draw	CF97	EXX	Load the draw colour.
	CF98	LD B,A
	CF99	EXX
	CF9A	PUSH HL	Draw the entity sprite.
	CF9B	CALL Draw_Wide_Entity_Sprite_Pixels_Only
	CF9E	POP HL
Step_Wide_Entity_Approach_Advance_Six	CF9F	LD DE,$0006	Prepare to advance past this entity record.
Step_Wide_Entity_Approach_Advance	CFA2	ADD HL,DE	Advance to the next entity record and return.
	CFA3	RET	Advance to the next entity record and return.