Learning how to hack Amiga games.

[Shatterhand]

Let's say I'd like start trying to hack Amiga games on ADF format... simple stuff, like maybe changing the palette or trying to add 2nd button support for games that use the keyboard for that....

Where should I start look to learn this kind of stuff? And what kind of tools I'd need?

[BippyM]

Depends specifically what you want..

Action replay or winuae debugger is a good start

[Shatterhand]

I've never even touched Winuae debugger, but it does sound like a good start.

[BippyM]

The debugger isn't the easiest to use. I'd start messing with a replay and find palette info, mess with sprites etc.

Wouldbe nice if there was a decent guide for the winuae debugger

[jotd]

then once you figured out what to change most of the time you have to add code to change it, because data & code is often packed and unpacked by the game only when needed.

Or unpack, change, repack, insert into adf image, and hope the packed size doesn't increase...

[malko]

Originally Posted by bippym

[...] wouldbe nice if there was a decent guide for the winuae debugger

+1

[BippyM]

Originally Posted by jotd

then once you figured out what to change most of the time you have to add code to change it, because data & code is often packed and unpacked by the game only when needed.

Or unpack, change, repack, insert into adf image, and hope the packed size doesn't increase...

Indeed, but one step at a time.. Learnt how Amiga works internally

[jotd]

A collaboration is also possible: you figure out what to change and we integrate that in whdload slaves for instance.

Earok does a lot of (excellent) game hacking but doesn't want to update whdload slaves. In that case, he just sends me his code with the addresses & where to patch and I integrate it (Ruff'n'tumble joypad support for instance).

You can start by trying to add trainers. This is the easiest thing to do I can think off. Levelskips are very useful, but a little trickier.

[BippyM]

Originally Posted by jotd

A collaboration is also possible: you figure out what to change and we integrate that in whdload slaves for instance.

Earok does a lot of (excellent) game hacking but doesn't want to update whdload slaves. In that case, he just sends me his code with the addresses & where to patch and I integrate it (Ruff'n'tumble joypad support for instance).

You can start by trying to add trainers. This is the easiest thing to do I can think off. Levelskips are very useful, but a little trickier.

I remember figuring out rainbow islands many years ago.. 4 rainbows anyone lol

[meynaf]

IMO the easiest way could be to re-source some system friendly game.
Then inserting/deleting code becomes a lot easier (and perhaps debugging as well).

[Sim085]

Do you mean like using tools like re-source?

Also what would you qualify as "system friendly"? For example would a game that runs from workbench be classified as so?

Originally Posted by meynaf

IMO the easiest way could be to re-source some system friendly game.
Then inserting/deleting code becomes a lot easier (and perhaps debugging as well).

[malko]

Originally Posted by Sim085

[...] Also what would you qualify as "system friendly"? For example would a game that runs from workbench be classified as so?

I would think so. Like Lucas or Sierra's adventure games.

Meynaf would better know but I think some games that are executable from WB (thus HD), WHDLoad games excepted, are not so system friendly and they, kind of "save" the system state before restoring it upon quitting. Am I correct ?

[meynaf]

Originally Posted by Sim085

Do you mean like using tools like re-source?

Yes.

Originally Posted by Sim085

Also what would you qualify as "system friendly"? For example would a game that runs from workbench be classified as so?

System friendly means it runs without destroying the OS, and actually uses it. In the ideal case, a game that can even multitask, which means you can use any amiga tool while the game is running.

Originally Posted by malko

I would think so. Like Lucas or Sierra's adventure games.

Meynaf would better know but I think some games that are executable from WB (thus HD), WHDLoad games excepted, are not so system friendly and they, kind of "save" the system state before restoring it upon quitting. Am I correct ?

Mere fact of being able to execute from WB does indeed not mean system friendly. Note that whdload games are not really to be considered system friendly because whdload actually saves the system state and restores it upon quitting.

[ross]

What wrote meynaf is right, but it's not always true for everyone.
That it is simpler to hack a system friendly game is subjective.
I prefer those who take over the system, I can better keep the situation under control .
Undoubtedly, you need to have a thorough knowledge of the hardware and debug tools are much less 'friendly'.

[meynaf]

Originally Posted by ross

What wrote meynaf is right, but it's not always true for everyone.
That it is simpler to hack a system friendly game is subjective.
I prefer those who take over the system, I can better keep the situation under control .
Undoubtedly, you need to have a thorough knowledge of the hardware and debug tools are much less 'friendly'.

If you use the emulator's debugger rather than an amiga one (i don't), then the situation becomes different.

But anyway that depends how much the game is "unfriendly" and how far you push "hacking". If it uses absolute addressing and you want to act at source level, believe me, it's not easy to insert/delete code.

[jotd]

One thing I did: I disassembled an executable (Battle Chess), figured out data (text) mistaken as source. Once all those fake sources were converted into data, I could reassemble/add/remove stuff.

This is the easiest (sometimes there are even symbols left in the executable ). If you need to hack NDOS games, the best is to improve existing whdload installs, as whdload slaves are designed to patch games easily.

There are a lot of slaves with enhancement requests, check whdload mantis for this.