Chase H.Q.: Routine at BDC1

BDC1: Clears screen then sets in-game attributes

Used by the routines at load_stage, run_pregame_screen and setup_game.
clear_screen_set_attrs	BDC1	CALL clear_game_screen	Call clear_game_screen
	BDC4	LD HL,$4800	Clear the game screen pixels to $FF (redoes similar work just done)
	BDC7	LD DE,$4801
	BDCA	LD BC,$0FFF
	BDCD	LD (HL),$FF
	BDCF	LDIR
	BDD1	LD HL,$5900	Clear the game screen attributes to $28 (black over cyan) - first two rows only
	BDD4	LD DE,$5901
	BDD7	LD (HL),$28
	BDD9	LD C,$40
	BDDB	LDIR
	BDDD	LD (HL),$68	Clear the next three rows to $68 (black over bright cyan)
	BDDF	LD C,$60
	BDE1	LDIR
	BDE3	LD A,($5CF4)	Clear the next 11 rows to the current ground colour
	BDE6	LD (HL),A
	BDE7	LD BC,$015F
	BDEA	LDIR
	BDEC	LD HL,$5900	Clear the edges of the game screen to black on black
	BDEF	LD DE,$001F
	BDF2	LD B,$10
clear_screen_set_attrs_0	BDF4	LD (HL),D
	BDF5	ADD HL,DE
	BDF6	LD (HL),D
	BDF7	INC HL
	BDF8	DJNZ clear_screen_set_attrs_0
	BDFA	RET	Return