emulator: Boytacean
type: libretro
source: "https://github.com/joamag/boytacean"
profiled_date: "2026-03-18"
core_version: "0.10.13"
display_name: "Nintendo - Game Boy / Color (Boytacean)"
cores:
  - boytacean
systems:
  - nintendo-gb
  - nintendo-gbc

notes: |
  Boytacean is a Game Boy / Game Boy Color emulator written in Rust by Joao Magalhaes.
  No external BIOS or boot ROM files are needed.

  The core ships with multiple boot ROMs compiled directly into the binary as static
  byte arrays in src/data.rs. For DMG mode the default is "DMG Bootix" (an open-source
  boot ROM forked from SameBoy's Bootix project, 256 bytes). For CGB mode the default
  is "CGB Boytacean" (a custom open-source CGB boot ROM, 2304 bytes). The original
  Nintendo DMG, SGB, and CGB boot ROMs are also embedded as static arrays (DMG_BOOT,
  SGB_BOOT, CGB_BOOT) but the defaults use the open-source replacements.

  The libretro frontend (frontends/libretro/src/core.rs) calls instance.load(true) in
  retro_load_game(), which routes through load_dmg() or load_cgb() depending on the
  cartridge header. These call load_boot_static() which copies one of the embedded byte
  arrays into MMU memory. There is no RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY call, no
  filesystem access for boot ROMs, and no core option to load external boot ROM files.

  The .info file (boytacean_libretro.info) lists no firmware entries.

  Boot ROM selection defaults:
  - DMG: BootRom::DmgBootix (gb.rs:1389) - open-source, 256 bytes
  - CGB: BootRom::CgbBoytacean (gb.rs:1398) - open-source, 2304 bytes

  All boot ROM source code lives in src/boot/, forked from SameBoy and assembled
  with rgbds. The compiled binaries are then converted to Rust const arrays in data.rs.

files: []

analysis:
  embedded_boot_roms:
    dmg_boot:
      constant: DMG_BOOT
      size: 256
      description: "Original Nintendo DMG boot ROM (embedded, not default)"
      source_ref: "data.rs:14-27"
    sgb_boot:
      constant: SGB_BOOT
      size: 256
      description: "Super Game Boy boot ROM (embedded, not default)"
      source_ref: "data.rs:29-42"
    dmg_bootix:
      constant: DMG_BOOTIX
      size: 256
      description: "Open-source DMG boot ROM from Bootix project (default for DMG)"
      source_ref: "data.rs:44-57"
    mgb_bootix:
      constant: MGB_BOOTIX
      size: 256
      description: "Open-source MGB (Game Boy Pocket) boot ROM from Bootix project"
      source_ref: "data.rs:59-72"
    cgb_boot:
      constant: CGB_BOOT
      size: 2304
      description: "Original Nintendo CGB boot ROM (embedded, not default)"
      source_ref: "data.rs:74-175"
    cgb_boytacean:
      constant: CGB_BOYTACEAN
      size: 2304
      description: "Custom open-source CGB boot ROM (default for CGB)"
      source_ref: "data.rs:177-275"
  filesystem_access: false
  system_directory_used: false
  boot_rom_source: "src/boot/ (assembly, forked from SameBoy)"