Atic Atac: Routine at 9BEA

Used by the routine at ENTER_ROOM.

Looks the room up twice. Its own entry in ROOM_TABLE gives a colour and a shape number; the shape number then selects an entry in ROOM_SHAPES, which carries how far the player may walk and where the outline's geometry lives. Rooms therefore share outlines freely -- only the colour and the shape number are per-room.

Verified against a running game: in room $00 the table gives colour $42 and shape $00, shape $00 gives 56 by 56 and the two pointers SHAPE_VERTI_00 and SHAPE_EDGES_00, and the machine's own $5E1A, $5E1D and $5E1E read back $42, 56 and 56 with the attribute file filled with $42.

Used by the routine at ENTER_ROOM. Looks the room up twice. Its own entry in ROOM_TABLE gives a colour and a shape number; the shape number then selects an entry in ROOM_SHAPES, which carries how far the player may walk and where the outline's geometry lives. Rooms therefore share outlines freely -- only the colour and the shape number are per-room. Verified against a running game: in room $00 the table gives colour $42 and shape $00, shape $00 gives 56 by 56 and the two pointers SHAPE_VERTI_00 and SHAPE_EDGES_00, and the machine's own $5E1A, $5E1D and $5E1E read back $42, 56 and 56 with the attribute file filled with $42.
DRAW_ROOM	9BEA	XOR A
	9BEB	LD ($5E14),A
	9BEE	LD A,($EA91)	The room the player is in.
This entry point is used by the routine at TRAPDOOR_FALL.
DRAW_ROOM_A	9BF1	LD BC,ROOM_TABLE	Two bytes per room...
	9BF4	LD L,A	...so double the room number to index it.
	9BF5	LD H,$00
	9BF7	ADD HL,HL
	9BF8	ADD HL,BC
	9BF9	LD A,(HL)	First byte: the colour the whole room is drawn in.
	9BFA	INC HL
	9BFB	LD ($5E1A),A
	9BFE	EXX
	9BFF	LD HL,$5800	24 by 24 character cells -- the play area, the same extent CLEAR_PLAY_AREA blanks.
	9C02	LD BC,$1818
	9C05	LD A,($5E1A)
	9C08	CALL FILL_BLOCK	Flood the attribute file with the room's colour in one go.
	9C0B	EXX
	9C0C	LD L,(HL)	Second byte is the shape number; six bytes per shape, so multiply by 6 the cheap way, as x2 + x4.
	9C0D	LD H,$00
	9C0F	ADD HL,HL
	9C10	LD C,L
	9C11	LD B,H
	9C12	ADD HL,HL
	9C13	ADD HL,BC
	9C14	LD BC,ROOM_SHAPES
	9C17	ADD HL,BC
	9C18	LD A,(HL)	How far from the centre the player may walk -- MOVE_ACTOR reads these back out of $5E1D.
	9C19	INC HL
	9C1A	LD ($5E1D),A
	9C1D	LD A,(HL)	The vertical limit.
	9C1E	INC HL
	9C1F	LD ($5E1E),A
	9C22	LD E,(HL)	Where the shape's vertices are.
	9C23	INC HL
	9C24	LD D,(HL)
	9C25	INC HL
	9C26	LD A,(HL)	Where its edge list is.
	9C27	INC HL
	9C28	LD H,(HL)
	9C29	LD L,A
	9C2A	PUSH DE	The vertices are indexed through IX.
	9C2B	POP IX	The vertices are indexed through IX.
	9C2D	PUSH BC
This entry point is used by the routine at DRAW_OUTLINE.
OUTLINE_DONE	9C2E	POP BC