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WebAssembly

Unlike the Pico and AVR ports, the WebAssembly build carries the full toolchain — compiler and VM both — compiled to WASM and running entirely client-side in the browser. This is what powers Lumen Playground: there’s no server-side execution, so programs you write in the Playground never leave your machine unless you choose to export them.

What runs in-browser

  • The same compiler pipeline described in Compiler Pipeline, turning .lmn source into bytecode.
  • The same VM described in The Virtual Machine, executing that bytecode.
  • File open/save for both .lmn source and precompiled .bin bytecode, backed by the browser’s native file picker rather than a real filesystem.

Because it’s the full toolchain rather than a VM-only port, the WASM build doesn’t need the funcTable/0xD0–0xFF split that Pico and AVR use — it dispatches built-ins the same way desktop does.

Exporting programs as QR codes

The Playground can take a compiled .bin program and export it as a sequence of QR codes instead of (or alongside) a downloadable file. This exists specifically to bridge to targets that don’t have an easy file-transfer path of their own — most notably Lumen on Android, which imports programs by scanning a QR sequence rather than pulling a file off a filesystem.

The underlying chunking scheme is target-agnostic: a .bin file is split into indexed chunks small enough to fit in a single QR code, each carrying enough information (chunk index, total count, a CRC32 checksum) to be reconstructed in any scan order and validated for corruption. The same scheme has a desktop-side implementation too — see Lumen on Android for how the pieces fit together end to end.

Why this matters for the embedded/mobile split

Between the four non-desktop targets, WASM is really the odd one out in a useful way: it’s the only port that both compiles and is reachable from a phone camera. That combination is what makes it the natural bridge for getting a Lumen program from “written on a laptop” to “running on Android” without ever touching a cable, a file share, or a server.