Chase H.Q.: Routine at 9DF4

9DF4: Toggle the light's BRIGHT bit (HL -> attrs)

Used by the routines at bonus_string and perp_sighted.
toggle_light_brightness	9DF4	LD BC,$0440	B = 4, C = $40 (BRIGHT bit)
toggle_light_brightness_0	9DF7	LD A,(HL)	Toggle attribute byte on five successive locations
	9DF8	XOR C
	9DF9	LD (HL),A
	9DFA	INC L
	9DFB	LD A,(HL)
	9DFC	XOR C
	9DFD	LD (HL),A
	9DFE	INC L
	9DFF	LD A,(HL)
	9E00	XOR C
	9E01	LD (HL),A
	9E02	INC L
	9E03	LD A,(HL)
	9E04	XOR C
	9E05	LD (HL),A
	9E06	INC L
	9E07	LD A,(HL)
	9E08	XOR C
	9E09	LD (HL),A
	9E0A	LD A,L	Move to next attribute row
	9E0B	ADD A,$1C
	9E0D	LD L,A
	9E0E	DJNZ toggle_light_brightness_0	Repeat for four rows
	9E10	RET	Repeat for four rows