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Building the ISO

tools/build_mod.py turns an untouched disc image into a patched one. It never writes to the source, and it is deterministic: the same inputs give the same output, so the build is the only place changes exist. Nothing is ever hand-patched into an ISO.

python tools/build_mod.py                              # find the original by CRC, write "<name> [Modded].iso"
python tools/build_mod.py --src my.iso --out out.iso
python tools/build_mod.py --include tools/rig/testops  # add extra recipes (test-only ones, say)
python tools/verify_iso.py original.iso modded.iso     # check the result

The steps​

  1. Tools. Build twinsdump if its source is newer than the binary.
  2. Level edits. Apply every mod/levels/*.ops recipe (plus any --include directories, plus mod/skip_prompt.ops last) to the original .rm2 files, and splice the edited script items back in.
  3. Text. Apply mod/text.txt to the language files - that is where the "hold △ to skip" string comes from.
  4. Materials. Switch the shadow-receiver flag on for crate materials (tools/materials.py).
  5. Executable patches. Apply mod/elf_patches.txt, checking every original word first.
  6. Disc layout. Move CRASH.BD to the end of the image and pack the files that followed it down into its old place, updating ISO 9660 and UDF.
  7. Rebuild CRASH.BD / CRASH.BH with the edited level files, and write the .pnach for the new CRC.

Each step prints what it changed, including the byte delta for every level file - which is the quickest way to spot a recipe that did nothing.

Why a recipe and not a patched file​

Level files are large and mostly opaque. Keeping the edit rather than the result means:

  • the repository contains no game data,
  • a change can be read and reviewed as four lines of text,
  • the same recipes can be applied to a freshly dumped disc, or to a different build, and will fail loudly rather than silently corrupt if the data underneath is not what was expected.

What the ISO ends up with​

  • Executable patches for the skip, the fixes and the timing changes.
  • Level recipes for the scenes whose skip wiring was cut, and for the contact-damage fix.
  • The skip prompt in five languages.
  • Crate materials marked as shadow receivers.
  • CRASH.BD at the fast edge of the disc.

Everything else on the disc is byte-identical to the original, and verify_iso.py proves it.