Atic Atac: Routine at A240

Used by the routine at ENTER_ROOM.

The third and last step of a room change, after CLEAR_PLAY_AREA and DRAW_ROOM. It writes attributes only -- the scroll, the timer and the score are drawn elsewhere and simply take whatever colour is underneath them, which is why walking into a differently-coloured room recolours the whole panel without anything being redrawn.

The colour is the room's own ink complemented: CPL then AND $07 keeps just the three ink bits and inverts them, so a red room gives a cyan panel, green gives magenta and so on. Complementing also throws away the bright and paper bits, which is why the panel comes out one shade darker than the room outline.

Inks 0 and 1 -- black and blue -- would be unreadable against black paper, so anything below 2 is replaced outright by $44, bright green. Measured by writing each room colour into $5E1A in turn and re-running: $42 gives $05, $43 gives $04, $44 gives $03, $45 gives $02, and $46 and $47 both give $44.

Used by the routine at ENTER_ROOM. The third and last step of a room change, after CLEAR_PLAY_AREA and DRAW_ROOM. It writes attributes only -- the scroll, the timer and the score are drawn elsewhere and simply take whatever colour is underneath them, which is why walking into a differently-coloured room recolours the whole panel without anything being redrawn. The colour is the room's own ink complemented: CPL then AND $07 keeps just the three ink bits and inverts them, so a red room gives a cyan panel, green gives magenta and so on. Complementing also throws away the bright and paper bits, which is why the panel comes out one shade darker than the room outline. Inks 0 and 1 -- black and blue -- would be unreadable against black paper, so anything below 2 is replaced outright by $44, bright green. Measured by writing each room colour into $5E1A in turn and re-running: $42 gives $05, $43 gives $04, $44 gives $03, $45 gives $02, and $46 and $47 both give $44.
PAINT_PANEL	A240	LD HL,$00C0	x = 192, the first character column past the play area.
	A243	CALL PIXEL_TO_ATTR	x = 192, the first character column past the play area.
	A246	LD BC,$0818	8 columns wide, 24 rows deep -- the rest of the screen.
	A249	LD A,($5E1A)	The room's colour, inverted.
	A24C	CPL
	A24D	AND $07
	A24F	CP $02	Too dark to read against black...
	A251	JR NC,PAINT_PANEL_0	Too dark to read against black...
	A253	LD A,$44	...so use bright green instead.
PAINT_PANEL_0	A255	LD E,A
	A256	PUSH DE
PAINT_PANEL_1	A257	PUSH BC
	A258	PUSH HL
PAINT_PANEL_2	A259	LD (HL),E	Fill one row of the panel.
	A25A	INC L
	A25B	DJNZ PAINT_PANEL_2
	A25D	POP HL
	A25E	LD BC,$0020	32 bytes to the row below.
	A261	ADD HL,BC	32 bytes to the row below.
	A262	POP BC
	A263	DEC C
	A264	JR NZ,PAINT_PANEL_1
	A266	LD HL,$90C8	The little blocks below the scroll are coloured separately...
	A269	CALL PIXEL_TO_ATTR
	A26C	LD A,($5E1A)	...in the room's own colour rather than the complement.
	A26F	LD BC,$0303
	A272	CALL FILL_BLOCK
	A275	INC L
	A276	LD (HL),A
	A277	ADD HL,DE
	A278	LD BC,$0202
	A27B	CALL FILL_BLOCK
	A27E	LD HL,$98D0	One cell on its own.
	A281	CALL PIXEL_TO_ATTR
	A284	POP DE
	A285	LD (HL),E
	A286	LD HL,$7DC8
	A289	CALL PIXEL_TO_ATTR
	A28C	LD BC,$0603	Bright white, for the part that never changes.
	A28F	LD A,$47	Bright white, for the part that never changes.
	A291	CALL FILL_BLOCK
	A294	LD HL,$5FC8
	A297	CALL PIXEL_TO_ATTR
	A29A	LD BC,$0604
	A29D	LD A,$46
	A29F	CALL FILL_BLOCK
	A2A2	LD HL,$48C8
	A2A5	CALL PIXEL_TO_ATTR
	A2A8	LD BC,$0601
	A2AB	LD A,$45
	A2AD	CALL FILL_BLOCK
	A2B0	LD BC,$0601
	A2B3	LD A,$47
	A2B5	CALL FILL_BLOCK
	A2B8	LD HL,$38C8
	A2BB	CALL PIXEL_TO_ATTR
	A2BE	LD BC,$0601
	A2C1	LD A,$43
	A2C3	CALL FILL_BLOCK
	A2C6	LD BC,$0601
	A2C9	LD A,$47
	A2CB	JP FILL_BLOCK