Retro/c64-elite-flicker-free
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Fixed a typo

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Mark Moxon 2022-09-06 11:24:17 +01:00
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@ -132,9 +132,9 @@ The Commodore Plus/4 version of Elite is an unofficial release of the game that
The patching process follows a similar set of steps to the Commodore 64 version, but it operates on a game binary that's already been extracted from Pigmy's original version (thank you to @Kekule1025 for doing this, and for packing the final game up after I'd done my patching). The game runs at a different address to the Commodore 64 version, so the [`elite-flicker-free-plus4.asm`](src/elite-flicker-free-plus4.asm) and [`elite-modify-plus4.py`](src/elite-modify-plus4.py) files modify the code in different places to the Commodore 64 version. Most (though not all) routines run at addresses that are $0900 higher in memory than their Commodore 64 counterparts, so that's why you can see `+ $0900` throughout these files.
Also, because the Pigmy version comes with a demo loading screen that takes up a fair amount of extra memory, we can't just tack the flicker-free routines onto the end of the game binary, as we do in the Commodore 64 version. Instead we can put them in the spite area, and specifically over the top of the two Trumble sprites, which are not used in the Plus/4 version (the Plus/4 does contain Trumbles, but because the machine does not support hardware sprites, they do not appear on-screen, and the sprite definitions are unused).
Also, because the Pigmy version comes with a demo loading screen that takes up a fair amount of extra memory, we can't just tack the flicker-free routines onto the end of the game binary, as we do in the Commodore 64 version. Instead we can put them in the spite area, and specifically over the top of the two Trumble sprites, which are not used in the Plus/4 version (the Plus/4 does contain Trumbles, but because the machine does not support hardware sprites, they do not appear on-screen, so the sprite definitions are unused and we can use the space to store the flicker-free routines).
The build process for the Plus/4 creates a file called `elite_+4_modified.prg` in the `work` folder that contains the modified game (you can load this into an emulator, and run it with a `SYS 20736`' command, as the game code starts at $5100). The downloadable version is wrapped in Pigmy's original demo and packing code, which is a process that is out of the scope of this site (I don't know how @Kekule1025 did it!).
The build process for the Plus/4 creates a file called `elite_+4_modified.prg` in the `work` folder that contains the modified game (you can load this into an emulator, and run it with a `SYS 20736` command, as the game code starts at $5100). The downloadable version is wrapped in Pigmy's original demo and packing code, which is a process that is out of the scope of this site (I don't know how @Kekule1025 did it!).
Apart from these differences, the patching process is the same as for the Commodore 64 version.