Planes draws

A canvas runtime that adds nothing to the language: a program draws by emitting show lines carrying the versioned drawing protocol — every line prefixed draw, thirty-four verbs, OKLCH colour (see the footer) — usually through use draw's helpers rather than assembled by hand, and the page paints them. Input crosses in as a value, not an effect; state crosses the tick boundary through write state to "state.json", one direction. The effect surface beside the canvas is computed, not declared — the same analyser try.html uses, now following use across the module graph too — and it is never hidden.

There are two renderers now, and the program cannot tell which is listening. The canvas below and the SVG the Save button writes walk the same stream through the same module; only what they do with a circle differs. That is what the protocol is for.

program:

arrow keys steer snake while it is playing · click the canvas to give it keyboard focus

SVG and PNG save the frame on screen now. Video records ten seconds.

effect surface — computed, not run:

(loading…)

source (editable — Run/Play use whatever is here):

base: — · modules: (none loaded)

output — lines the program showed that were not draw commands, or an error:

(no output yet)

Drawing Protocol v3 — thirty-four verbs, every line prefixed draw: colour and line (stroke, fill, width, cap, corner, alpha, dash, blur), shapes (line, rect, circle, ellipse, arc, triangle — rect/ellipse take an optional rotation), paths (shape, vertex, curve, close, end), transforms (push, pop, translate, rotate, scale), text and canvas (label, size, align, background, clear), and paint and compositing (gradient, shadow, blend, clip, unclip). Colour is OKLCH (L C H, plus A for stroke/fill). A line not beginning with draw goes to the output pane as text, unconditionally; a line that does begin with draw is always a command, and a malformed one is reported as an error rather than drawn. A stream declares its version — draw protocol 1, draw protocol 2, or draw protocol 3, or nothing (version 1) — and a verb introduced in a later version, used without declaring it, is refused rather than silently drawn. The one exception: an optional argument that widens an existing verb's arity (the rotation on rect/ellipse, the inner radius on gradient radial) is accepted regardless of the declared version — it adds no new verb, so there is nothing for a version to gate.

Two renderers. The canvas and the SVG exporter are sinks for one stream walk (js/paint/stream.mjs): the version declaration, the path lifecycle, transform balance, the arc convention and every error tag are written once and shared, so the two cannot drift apart. Saving. SVG and PNG capture the frame that is on screen — for a program that redraws continuously that is a snapshot, not an animation. PNG is written at twice the device pixel ratio. Video records ten seconds of the canvas as WebM. A saved SVG's labels are laid out by whatever font resolves where the file is opened, so text may shift on another machine; both renderers name the same family, and nothing can make that hold everywhere.

Opens directly in Safari or Firefox. Chrome blocks ES-module loading over file:// as a security policy — for Chrome, serve the folder with python3 -m http.server and open http://localhost:8000/paint.html. No bundler, no transpiler, no network dependency: the page loads the real js/*.mjs modules, the real grammar/*.json as JSON modules, and the paint/*.planes programs and libraries as plain text, all from this same directory.

After an update. The .planes files carry a per-visit token and are never served stale. The .mjs modules cannot: giving them one would mean rewriting every import URL, which needs a build step this page does not have. If a browser ever serves a mix of old and new modules, the page says so in the output pane and names the one thing that fixes it — in Safari, Develop → Empty Caches, because a plain reload keeps ES modules.