Chase H.Q.: Routine at FEA9

Prints the title/prompt text and the 8 control-name labels (FC29: gear, accelerate, brake, left, right, quit, pause, turbo) via print_string, then for each of the 8 controls in turn (BC=$0801 at FEBE) waits for a fresh keypress (read_new_key_definition) and stores the chosen key, redrawing its name on screen.

Hidden test-mode unlock ($FEE2-$FEF1): compares the 8 keys just chosen against a fixed 8-byte reference sequence at $FFEF (in the same scan-key-code encoding documented at read_new_key_definition). Decoding those 8 bytes through that encoding spells S, H, O, C, K, E, D, ENTER -- i.e. this is a hidden cheat code: redefining the 8 controls to spell "SHOCKED" followed by ENTER. On any mismatch the loop's RET NZ returns immediately (the ordinary case -- the new key mapping is simply kept and control returns to the caller, options_menu_driver). On an exact match it falls through, sets the test-mode/cheat flag at $8000 (see 84C2 in the main skool), shows a "TEST ... CHASE H.Q. TEST MODE" confirmation ($FCF0 text) and waits for fire, then loops back to $FEA9 to redisplay the redefine-keys screen (there is no path back to the caller once the secret code has been entered other than through this routine itself).

Used by the routine at options_menu_driver.

Prints the title/prompt text and the 8 control-name labels (FC29: gear, accelerate, brake, left, right, quit, pause, turbo) via print_string, then for each of the 8 controls in turn (BC=$0801 at FEBE) waits for a fresh keypress (read_new_key_definition) and stores the chosen key, redrawing its name on screen. Hidden test-mode unlock ($FEE2-$FEF1): compares the 8 keys just chosen against a fixed 8-byte reference sequence at $FFEF (in the same scan-key-code encoding documented at read_new_key_definition). Decoding those 8 bytes through that encoding spells S, H, O, C, K, E, D, ENTER -- i.e. this is a hidden cheat code: redefining the 8 controls to spell "SHOCKED" followed by ENTER. On any mismatch the loop's RET NZ returns immediately (the ordinary case -- the new key mapping is simply kept and control returns to the caller, options_menu_driver). On an exact match it falls through, sets the test-mode/cheat flag at $8000 (see 84C2 in the main skool), shows a "TEST ... CHASE H.Q. TEST MODE" confirmation ($FCF0 text) and waits for fire, then loops back to $FEA9 to redisplay the redefine-keys screen (there is no path back to the caller once the secret code has been entered other than through this routine itself). Used by the routine at options_menu_driver.
redefine_keys_screen	FEA9	CALL clear_options_screen
	FEAC	LD HL,$FC9B
	FEAF	CALL print_string
	FEB2	CALL run_title_tune
	FEB5	LD HL,$FCC9
	FEB8	CALL print_string
	FEBB	LD DE,$48D6
	FEBE	LD BC,$0801
redefine_keys_screen_0	FEC1	PUSH HL
	FEC2	PUSH DE
	FEC3	PUSH BC
	FEC4	CALL run_title_tune
	FEC7	POP BC
	FEC8	POP DE
	FEC9	POP HL
	FECA	XOR A
	FECB	IN A,($FE)
	FECD	CPL
	FECE	AND $1F
	FED0	JR NZ,redefine_keys_screen_0
	FED2	CALL read_new_key_definition
	FED5	INC C
	FED6	INC HL
	FED7	DJNZ redefine_keys_screen_0
	FED9	LD B,$14
redefine_keys_screen_1	FEDB	PUSH BC
	FEDC	CALL run_title_tune
	FEDF	POP BC
	FEE0	DJNZ redefine_keys_screen_1
	FEE2	LD B,$08	"SHOCKED"+ENTER secret-code check (see block header)
	FEE4	LD DE,$FFEF	DE -> fixed reference key sequence
	FEE7	LD HL,$FFF7	HL -> the 8 keys just chosen
redefine_keys_screen_2	FEEA	LD A,(DE)
	FEEB	CP (HL)
	FEEC	INC HL
	FEED	INC DE
	FEEE	RET NZ	Mismatch -> ordinary case, return to caller
	FEEF	DJNZ redefine_keys_screen_2
	FEF1	LD A,$01	All 8 matched -> enable test mode
	FEF3	LD ($8000),A
	FEF6	CALL clear_options_screen
	FEF9	LD HL,$FCF0
	FEFC	CALL print_string
redefine_keys_screen_3	FEFF	CALL run_title_tune
	FF02	XOR A
	FF03	IN A,($FE)
	FF05	CPL
	FF06	AND $1F
	FF08	JR Z,redefine_keys_screen_3
	FF0A	JR redefine_keys_screen