Thexder keyboard commands

Champion (344)

10-01-2021, 01:03

I have disassembled Thexder to check for keyboard commands (call $0141) and I have found the following keys/combination
ESC+Q: kill character (end the game)
STOP: pause game
SHIFT: activate shield
SPACE: fire laser
UP,DOWN,LEFT,RIGHT: move character
SELECT+A+O+W: set 1 to the address $F2e9 but I couldn't figure out the effect of such combination on the game.

6702 :	3E 02		LD	A,#$02		; 
6704 :	CD 41 01	CALL	$0141		; BIOS_SNSMAT
6707 :	FE BF		CP	#$BF		; 
6709 :	C0		RET	NZ		; 
670A :	3E 04		LD	A,#$04		; 
670C :	CD 41 01	CALL	$0141		; BIOS_SNSMAT
670F :	FE EF		CP	#$EF		; 
6711 :	C0		RET	NZ		; 
6712 :	3E 05		LD	A,#$05		; 
6714 :	CD 41 01	CALL	$0141		; BIOS_SNSMAT
6717 :	FE EF		CP	#$EF		; 
6719 :	C0		RET	NZ		; 
671A :	3E 07		LD	A,#$07		; 
671C :	CD 41 01	CALL	$0141		; BIOS_SNSMAT
671F :	FE BF		CP	#$BF		; 
6721 :	C0		RET	NZ		; 
6722 :	3E 01		LD	A,#$01		; 
6724 :	32 E9 F2	LD	($F2E9),A	; 
6727 :	C9		RET

Haven't seen any changes while running the game on OpenMSX or WebMSX
Haven't seen any changes either by poking addres 0xf2e9 in openmsx.

Any clues ?

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Van Pencioner

Scribe (1611)

10-01-2021, 02:07

My guess - might be a leftover after removing debug feature or some part not included in final game... (it happens quite often in software world)

Van larsthe18th

Master (192)

10-01-2021, 05:01

I think i have got it,
First push [STOP] key to pause the game, then push [SELECT] + [A] + [O] + [W]
- Your health wil be restored to 100%
push [STOP] key again to continue the game.

Funny thing is, this only works once.
Adress $F2E9 has value 01 if cheat is used, this will reset after Game Over.

If you load the ROM in a HEX editor, you will read the following.
MADE BY WAO ISEE SPECIAL THANKS - M.MIYAMOTO JEMINI JAN LUNARIAN PAL PAC MOO

P.s. The key combination above wil not work in emulation, use a real MSX.

Van Danjovic

Champion (344)

10-01-2021, 04:33

Thanks @larsthe18th. I will try in the real machine as soon as I can.

Van larsthe18th

Master (192)

10-01-2021, 04:58

In OpenMSX you can use a TLC script to push [SELECT] + [A] + [O] + [W] buttons.
you only have to push [STOP] and lauch the thex script in console.

set_help_text thex "Thexder Cheat."

proc thex {} {

			keymatrixdown 7 64
			keymatrixdown 5 16
			keymatrixdown 4 16	
			keymatrixdown 2 64			
			
			after time 2 {
				keymatrixup 2 64
				keymatrixup 4 16
				keymatrixup 5 16
				keymatrixup 7 64			
			}		
		}

Van Manuel

Ascended (19685)

10-01-2021, 11:35

Why isn't it working when using the actual keyboard?

Van Randam

Paragon (1431)

10-01-2021, 12:51

Those special thanks are all Compile people. Did Compile also work on it?

Van turbor

Hero (529)

10-01-2021, 13:44

Manuel wrote:

Why isn't it working when using the actual keyboard?

I assume this is due to key ghosting. Nice video here https://www.youtube.com/watch?v=iWuqWhw8E4Q
My PC keyboard for instance refuses to register spacebar when I have cursor-up and cursor-left already pressed (Darn pretty annoying when playing nemesis, I can't shoot when retreating to the upper left corner... ;( )

Van Danjovic

Champion (344)

10-01-2021, 15:12

I have tested again on WebMSX and it worked. I may have missed the need to have the game in STOP. Maybe the probl
I assume that the address 0xf2e9 is used to mark that the trick was already used, as it only work once.

And indeed, ghosting prevent it for working on OpenMSX. I have verified that the combination F8+A+O+W is not possible to obtain in my keyboard (https://www.redragon.com.br/antighosting).

Thanks all you guys!

Van Manuel

Ascended (19685)

10-01-2021, 18:09

But F7 is select, not F8... that's STOP.

Van Danjovic

Champion (344)

10-01-2021, 18:43

Manuel wrote:

But F7 is select, not F8... that's STOP.

Sorry, typo mistake. my PC keyboard does not accept F7+A+O+W at the same time.