0.4.7

This release adds tile replacement: the backgrounds and level art can be replaced with PNG files.

• Tile replacement (Issue #35): the Mega Drive layer's 8×8 tiles can be replaced with PNG files, no ROM hacking tools needed.

  1. Turn on OPTIONS > EXTRAS > DUMP TILES and play the part you want to change. Each tile the game draws is saved once to Mods/Textures/Dump as md_<hash>.png, a palette-indexed PNG with the palette it was drawn with.
  2. Copy the tiles you want to change into Mods/Textures, keeping their names, and edit them. Keep them 8×8 and indexed.
  3. Each one is drawn instead of the original, wherever the game uses that tile.

  Notes:

  • A tile is recognised by its pixels, not by where it sits in video memory.
  • The PNG's colours are indices into the game's palette (0 is transparent), so fades and palette cycling still apply.
  • Only the picture changes. The game's view of the hardware, including sprite collisions, still comes from the original tiles, so it plays exactly as before. A pack made of a level's own tiles gives pixel-identical pictures, and the recompiled code stays bit-identical to the interpreter with a pack loaded.

  This covers the Mega Drive layer: backgrounds and level art. The characters, the HUD, objects and the title screen are drawn by the 32X in software and are not covered yet. How that layer is drawn, and the plan for replacing it, is in docs/SPRITES_32X.md. Details: docs/TEXTURE_MODS.md.

• For developers: chaotix_headless --layer md|32x renders one display layer alone. Its --tiles DIR and --dump-tiles DIR options do the same as the settings above. The interpreter-only build (without generated code) compiles again; 0.4.6 had broken it.

Thanks to @datadrivezz for the request.

Validation:

• Windows: all 31 CTest cases pass.
• Linux: all 28 Linux CTest cases pass.
• New tests: unit tests for tile replacement (sprite and plane tiles, transparency, collisions following the original tiles both ways, dumping) and for the new PNG reader and writer, plus tile_pack with the real ROM.
• Packages: the packaged Windows and Linux builds pass the startup tests, and dumping was checked in the app.
• Android: the APKs have not been tested on a device for this release.

Downloads: the Windows x64 zip, the Linux x64 tar.gz, and two Android APKs: arm64-v8a/x86_64 (the usual one) and armeabi-v7a (32-bit ARM). Both APKs use version code 20 and the same signing certificate as 0.4.6, so they update in place.

You must supply your own Knuckles' Chaotix (Japan, USA) ROM. No ROM image or game assets are included.