Chase H.Q.: Routine at 8876

Discards the user's input outright during a fade transition (transition_control 4). Otherwise it masks user_input with the stage's input mask and dispatches on the top three bits: quit starts the quit sequence at check_user_input_quit_key, pause spins until the key is released and then waits for any key before debouncing, and turbo arms 60 ticks of boost and starts the turbo chatter — but only if no boost is running and boosts remain.

Used by the routine at main_loop.

Discards the user's input outright during a fade transition (transition_control 4). Otherwise it masks user_input with the stage's input mask and dispatches on the top three bits: quit starts the quit sequence at check_user_input_quit_key, pause spins until the key is released and then waits for any key before debouncing, and turbo arms 60 ticks of boost and starts the turbo chatter — but only if no boost is running and boosts remain. Used by the routine at main_loop.
check_user_input	8876	LD A,($A231)	Load transition_control
	8879	LD HL,$A0D5	Load address of user_input
	887C	CP $04	Ignore the user's input if transition_control is set to 4
	887E	JR NZ,check_user_input_0	Ignore the user's input if transition_control is set to 4
	8880	LD (HL),$00	Clear user_input
	8882	RET	Return
check_user_input_0	8883	LD A,($A16F)	AND user_input with user input mask
	8886	AND (HL)
	8887	LD (HL),A
	8888	AND $E0	AND with mask for (Quit+Pause+Turbo), return if none
	888A	RET Z	AND with mask for (Quit+Pause+Turbo), return if none
	888B	RLA	Quit bit set? Jump to quit_key if so
	888C	JR C,check_user_input_quit_key	Quit bit set? Jump to quit_key if so
	888E	RLA	Pause bit set? Jump to pause_key if so
	888F	JR C,cui_pause_key	Pause bit set? Jump to pause_key if so
Turbo was pressed
	8891	LD HL,$A24E	Load address of boost timer
	8894	LD A,(HL)	Return if a turbo boost is in effect
	8895	AND A
	8896	RET NZ
	8897	LD A,($A170)	Return if no turbo boosts are left
	889A	AND A
	889B	RET Z
	889C	LD (HL),$3C	Set 60 ticks of boost
	889E	LD HL,$9917	HL -> Random choice of (WHOAAAAA! / GREAT! / ONE MORE TIME.)
	88A1	LD A,$02	Call start_chatter (priority 2)
	88A3	CALL start_chatter	Call start_chatter (priority 2)
	88A6	JP setup_engine_sfx_hook	Exit via setup_engine_sfx_hook
This entry point is used by the routine at check_time_up.
check_user_input_quit_key	88A9	LD A,($A26A)	If quit_state != 0 then return (quit in progress)
	88AC	AND A
	88AD	RET NZ
	88AE	CALL drive_chatter_stop	Call drive_chatter_stop
	88B1	CALL fill_attributes	Call fill_attributes
	88B4	LD ($A16F),A	user_input_mask = 0 -- A is zero from fill_attributes
	88B7	INC A	user_input_mask = 0 -- A is zero from fill_attributes
	88B8	LD ($A26A),A	quit_state = 1 -- start quitting
	88BB	RET	Return
cui_pause_key	88BC	CALL silence_audio_hook	Call silence_audio_hook
check_user_input_1	88BF	CALL keyscan	Call keyscan while PAUSE is pressed
	88C2	AND $40
	88C4	JR NZ,check_user_input_1
check_user_input_2	88C6	CALL keyscan	Call keyscan until keys are pressed (ignoring quit)
	88C9	AND $7F
	88CB	JR Z,check_user_input_2
check_user_input_3	88CD	CALL keyscan	Call keyscan until keys are released (debounce)
	88D0	AND $7F
	88D2	JR NZ,check_user_input_3
	88D4	RET	Return