Knight Lore: Routine at BD6C

BD6C: Start the game?

Used by the routines at check_for_directional_control and clr_debounce. Clicks if the control byte changed this pass, then returns to start the game if 0 is pressed. Otherwise it bumps the seed at $5BA0 -- so the time spent in the menu shapes the game that follows -- updates the flashing lines and goes round again.
check_for_start_game	BD6C	LD HL,$5BA6	A is the new control byte here, whichever way we arrived
	BD6F	CP (HL)
	BD70	CALL NZ,toggle_audio_hw_x16
	BD73	LD A,$EF	half-row $EF is 0 9 8 7 6; bit 0 is the 0 key
	BD75	CALL read_port
	BD78	BIT 0,A	CPL in read_port means a set bit is a pressed key
	BD7A	RET NZ
	BD7B	LD HL,$5BA0	one more step of the seed per pass of the menu
	BD7E	INC (HL)
	BD7F	CALL flash_menu	show the new selection and loop
	BD82	JP menu_loop	show the new selection and loop