This is an average implementation of Crossfire meets Solar Fox (a model 2600 title), this download is an executable file version of a cracked copy which started as a disk having bad (duplicate) sectors. Due to sloppy cracking which I want to talk about, this file is many thousands bytes longer than has to be. Why did the publisher think this average toy of a game deserved the expensive and time consuming duplicate sector protection? This game is actually 8K cartridge sized, the ONLY thing making it larger than 8K is the copy protection subroutine itself, checking a floppy disk fer redundant sector #120.
I used to admire (other) "code crackers" from the 1980s but after examining a lot of A8 software recently, I'm losing respect. Instead of going thru the Front Door and reading and tailoring code to each individual program, they en masse made "memory dumps" and used various utilities to apply annoying often useless patches to heads and tails of files, sometimes patched in batches there was such automation. They did the equivalent of "save state" an emulator can do, which has at least one flaw in that it might not randomize things the right way in repeat plays. And the non original patches show up sometimes nested 3 or even 4 layers thick. Like if someone used a utility to convert file to cassette, it might add a patch, and then, someone converts that cassette to disk and you get more patching instead of removing the 1st patch etc. For another example, "Megagun" has multiple useless patches (which can be removed) that prevented it from being recognized as a cartridge game.
"Parallax" is a single segment occupying memory addresses $1800 thru $38DB. The game traps the Reset button on its own, and begins running at $1800, it could run without a run segment since any single segment file meant to run at its beginning actual will run at the beginning if not told to run elsewhere, BUT it's always POLITE to specify a run segment. The download data won't work this way until modified, because tada: it wasn't really cracked. The "dumper" (not Cracker) got around actual cracking by supplying a Middle run address, the equivalent of "load state" to reciprocate the "save state" which created this file. Jumping past initialization routines is exactly the trouble I'm pointing out.
This Parallax download (10833 bytes long) can be converted to a more respectable cracked reduction 8424 bytes long. Skip the first 2080 bytes, copy out the next 8424 bytes, and discard the remaining 329 bytes of the 10833 byte file. Most of the discarded material is duplicates of stuff already in the 8424 (more confirmation that the Dump Method had been employed), plus useless non original patches. In the new file, change the first six bytes to read $"FF FF 00 18 DB 38" and change the last six bytes to $"E0 02 E1 02 00 18". New file won't function yet, because of the copy protection which needs cracking. First the disk checker subroutine was encrypted, but no longer is because of the Dump Method which made the 10833 big file, so we have to stop it from being scrambled a 2nd time. Change the sequence "$45 $BA" at new offset $83D to become "$49 $00". Lastly, change the byte at offset $16B7 from $"A9 01 8D 03 01" to replace A9 with $60, this bypasses the sector tests.