PATCH: Allowing the Pogo to always fly.

Completed patches for Keen1.
Yowza
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Post by Yowza » Sat Jan 29, 2005 12:18 am

I've been meaning to ask about a patch like this for a while :D... Although, I was thinking of using the ankh in Keen 3 instead. Not sure exactly how it would work... I suppose you'd make it so that the pogo/jetpack could only be activated when you have ankh. It'd also be nice to have it all in one button (Alt), instead of pressing Alt to turn it on and Ctrl to actually fly. Not sure how well that would work though...

What would be REALLY nice (although probably not possible) is that pogo usually works, except when you have ankh, in which case it'd turn into a jetpack. Even ignoring all the sprite problems, that probably wouldn't work though.

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levellord
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Post by levellord » Mon Feb 07, 2005 3:27 am

Here's another patch to stop your jetpack bouncing off the ground:

#Pogo stops when Keen hits the ground.
%patch $409B $90 $90


To hack these directly into the executable the adress for this patch is $429B, and for the origional jetpack patch it is $414E.

KeenRush
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Post by KeenRush » Mon Feb 07, 2005 11:14 am

For which Keen is that for? I haven't tried it, only checked what bytes it replaces, and doesn't make sense for me.

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levellord
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Post by levellord » Tue Feb 08, 2005 3:15 am

Keen 1.31, although I used a hexeditor that can be 'difficult' at times. I obtained it by getting the H.E to scan the executable and dumped versions of Keen 1 and matching their code. According to H.E it should replace the same code in the executable as the patch does in the dumped file.

lemm
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Post by lemm » Mon Aug 24, 2009 12:39 pm

Ringman wrote:I understand the need to only patch and not hex edit, but I don't plan on releasing this to the public.

Thanks for the patch, but I'm still lost as to how to use that in a hex editor as opposed to ckpatching.

I'm sure that $34fe is the address, but what is $90 $90? If I put 9090 in the game crashes when using the pogo. Please explain what value needs to be put here in the exe file.

Code: Select all

	// seg000:3F49
	if (MEMW(god_mode) != 0 && MEMW(word_1B01C) != 0) {
		// seg000:3F57
		W_MEMW(keen_pos_y, 0xff38);
	}
// http://www.quantumg.net/keen1.c.txt
$90 is the opcode for NOP (i believe).

and at 0x3F49...

Code: Select all

00003f49: cmp word [0x5daa], byte +0x0
00003f4e: jz 0x3f5d
which means if god mode = 0, jump past the rest of the if block, skipping W_MEMW(keen_pos_y, 0xff38), which is what makes the jetpack do its thing. So if you replace this cmp with nothing, the zero flag will not be set and the jetpack code will be called.

Disclaimer: I know dick all about programming; I am probably not right

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CommanderSpleen
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Post by CommanderSpleen » Mon Aug 24, 2009 1:19 pm

Woah! You actually found that file! Sveeeet. I recommend posting it somewhere(s) more prominent.

levellass
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Post by levellass » Tue Aug 25, 2009 6:42 am

Um.... what? Er... hurrah!

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CommanderSpleen
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Post by CommanderSpleen » Tue Aug 25, 2009 3:38 pm

http://www.quantumg.net/keen1.c.txt

Someone's reverse-engineered Keen 1 code!

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Tulip
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Post by Tulip » Tue Aug 25, 2009 5:38 pm

Nickssoft posted that one a while ago at the PCKF.

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CommanderSpleen
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Post by CommanderSpleen » Wed Aug 26, 2009 2:26 am

Wasn't the link down at the time though?

lemm
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Post by lemm » Wed Aug 26, 2009 2:33 am

Does anyone know how to do this for keens 2 and 3?

levellass
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Post by levellass » Wed Aug 26, 2009 6:34 am

Not me, though I do like to compare 2-3 with 1 for an idea of how things work. The executables are largely the same.

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