babeltro

How do you make a plasma in Perl? A tunnel in SQL? A fire in raw WebAssembly?

Nine classic demoscene effects — starfield, tunnel, plasma, rotozoom, metaballs, synthwave grid, fire, Mandelbrot, a logo card — written in thirteen languages and run live, side by side, in your browser. Every pixel is computed on the CPU, and every port draws the same pixels as the C reference, bit for bit. Babel for the languages, "-tro" for the intro.

Live: https://babeltro.storagebits.workers.dev

The point is not which language wins. It is what each one makes you write to produce the same image: float widths, fused multiply-adds, float-to-int conversion, bounds checks, evaluation order, the maths library — and, for some, the absence of a maths library.

What is in the lab

• Each language's hot loop under the canvas, next to a second language of your choice, with a one-line note on what each does differently.
• Optimisation ladders for the plasma, the tunnel and the Mandelbrot: the naive version first, then one trick at a time; any rung can run next to the last one, with a pixel diff: grey where they match, magenta where they do not.
• A race: every language on the current effect, timed, checked against the reference.

The languages

Language	Directory	How it gets into the browser	Effects
Go	go/	wasm, Go's own backend	9
TinyGo	ports/tinygo/	the same Go files, compiled through LLVM	9
C	ports/c/	clang + wasi-libc — the reference	9
C++	ports/cpp/	clang + libc++, C++23	9
Rust	ports/rust/	wasm32-unknown-unknown, no dependencies	9
Zig	ports/zig/	wasm32-freestanding, comptime tables	9
AssemblyScript	ports/assemblyscript/	asc, no imports	9
Raw WebAssembly	ports/wat/	written directly in WAT, no compiler; its own sin/atan2/exp, 14.5 KB	9
x86 assembly	ports/x86/	NASM machine code on a tiny 386+SSE emulator in wasm	9
JavaScript	ports/js/	plain ES modules, Math.fround everywhere	9
Python	ports/python/	CPython + NumPy in wasm (Pyodide)	9
Perl	ports/perl/	Perl 5.42 in wasm (zeroperl)	9
SQL	ports/sql/	SQLite in wasm (sql.js), one query per frame	9

Every effect a port implements is byte-identical to the reference at every size and rung tested. The one exception is by design: the finale spells the language's name, and its layout follows the name's width.

A few things the ports found:

• The timings measure compilers as much as languages. The same Go code is 1.5–3× faster built by TinyGo than by Go's own wasm backend, which keeps every function resumable for goroutines. Native Go is faster still.
• SQLite has no float32, so the SQL port emulates Go's float32 rounding in pure SQL with Veltkamp's split. Without it, a few hundred pixels a minute drift.
• x86 assembly runs on an emulator written for the occasion: 22 emulated instructions per plasma pixel, SSE only, because x87's 80-bit intermediates would break pixel identity.
• WebAssembly has no sin. The raw WAT port computes its sine table with a Cody-Waite reduction and a Taylor series: all 8193 entries match Go's bit for bit.
• Perl matches too, at a price: unpack 'f', pack 'f' after every float32 operation, a third of its frame time.
• The Pythonic plasma is not a loop: the NumPy version is 100–250× faster than the plain-Python rungs.

Each port's NOTES.md says what it does differently, effect by effect.

Running it

cd web
npm install
../scripts/build-all.sh   # builds every wasm port into web/public/wasm
npm run dev

The ports need their toolchains (LLVM with wasi-libc, Rust, Zig, TinyGo, AssemblyScript, wabt); the Perl port fetches its interpreter with ports/perl/fetch.sh. Python, Perl and SQL bring their interpreters as wasm and need nothing to build.

Keys: Space pause, ←/→ effect, . one frame, R restart, D differences (ladders), Esc home.

Checking a port

node tools/check.mjs go rust js                   # every effect against C
node tools/check.mjs --scene 2 --step 1 python    # one rung of a ladder
node tools/check.mjs --png /tmp/diff --size 160x90 perl

How it was made: the prompts are in PROMPTS.md and every decision is in DECISIONS.md. The contract every port follows, and how to add a language, is spec/ABI.md. What could come next is in docs/ROADMAP.md. go/ also still builds the original native demo (a window, a HUD, a worker pool): see go/README.md.

Licence

MIT — see LICENSE.