This is the existing Aesthetic Computer Game Boy stack made portable: kidlisp-gameboy/README.md → C-QUICKSTART.md → build.sh → GBDK lcc. The ROM output is intended for the existing AC WasmBoy runtime under system/public/aesthetic.computer/dep/wasmboy, or a compatible emulator/cart. It is real cartridge software, not a mock Game Boy skin or a new compiler.

hello.c is copied verbatim from kidlisp-gameboy/src/hello.c. starter.c is an original interactive sketch using that stack's documented vsync, joypad, and sprite patterns: move a diamond with the D-pad and recenter with A. No commercial ROM, Nintendo game assets, or boot ROM is bundled.

A project contains editable main.c, its gameboy.json recipe, and—only after a successful GBDK build—game.gb plus build.json provenance. GBDK creates the standard bootable cartridge header. Validation checks its logo, declared ROM size, header checksum and global checksum. The source and compiler binary hashes are saved with the ROM hash. Source edits keep the last successful preview and mark metadata.sourceAhead; export requires the source to match the build. The shared Aesel artifact history owns versioning and rollback.

Install GBDK-2020, following its getting-started guide. Set GBDK_HOME to the extracted gbdk directory. An explicitly configured but missing toolchain is an error, never silently substituted. Otherwise discovery checks the monorepo's kidlisp-gameboy/gbdk, Aesel's optional local GBDK 4.5.0 pack, then PATH. The optional pack location is ~/.local/share/aesel/toolchains/gbdk-4.5.0/gbdk.

Builds invoke the same lcc -o game.gb main.c workflow as AC, adding only a fixed AESEL cartridge title. They run in an isolated temporary artifact directory, with fixed arguments, no shell, no forwarded credential environment, a 20-second process-group timeout, and bounded diagnostics. Failed compiles preserve the previous ROM. Source paths and outputs reject symlinks; project file writes are confined to the artifact.

This first lane supports one GBDK C source, built-in SDK headers, original DMG hardware, and embedded arrays for graphics/audio. It deliberately rejects custom includes, inline assembly, compiler pragmas and token-pasting. It does not claim a hostile-compiler security sandbox, full KidLisp-to-ROM support, assembly editing, CGB bank management, or native compiler redistribution. Without GBDK, create still gives editable source and installation instructions; no ROM is fabricated.

Local validation used the official GBDK 4.5.0 macOS arm64 release, with archive SHA-256 289ee60e46c5a2785a21e35533f84a5131ed4a063b21b0dbdedc9a10af15bf78 matching its GitHub release asset digest. Both the original AC Hello source and the interactive starter compiled into verified 32768-byte cartridges.