Mandelbrot explorer · grok-build-0.1
Render the Mandelbrot set with a smooth color gradient on a full-screen canvas, with click-and-drag to pan and mouse-wheel to zoom.
transcript · 10 messages
Render the Mandelbrot set with a smooth color gradient on a full-screen canvas, with click-and-drag to pan and mouse-wheel to zoom.
thinking
The task is: "Build a single-page web app and write it ALL into one self-contained file named index.html in the current directory: CSS in a <style> tag, JS in a <script> tag, inline — do not create se...
{"command":"ls -la /tmp/ws"}total 0 drwxr-sr-x. 2 node node 6 Aug 1 20:15 . drwxrwsrwx. 3 root node 16 Aug 1 20:15 ..
thinking
The task is: "Build a single-page web app and write it ALL into one self-contained file named index.html in the current directory: CSS in a <style> tag, JS in a <script> tag, inline — do not create se...The task is to build a single-page web app in one index.html file with HTML, CSS in <style>, JS in <script>. It needs to render the Mandelbrot set on a full-screen canvas with smooth color gradient, click-and-drag to pan, mouse-wheel to zoom. No external resources.
I need to write the entire code for index.html.
First, structure:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Mandelbrot Set</title>
<style>
body { margin: 0; overflow: hidden; }
canvas { display: block; }
</style>
</head>
<body>
<canvas id="mandelbrot"></canvas>
<script>
// JS code here
</script>
</body>
</html>
For JS:
Use canvas, get context.
Handle resize: set canvas size to window size, use devicePixelRatio for high DPI.
To make it simple, ignore retina 2x, just use 1:1, but for full screen it's ok, but blurry, better handle.
For perf, let's use:
let canvas = document.getElementById('mandelbrot');
let ctx = canvas.getContext('2d');
function resize() {
canvas.width = window.innerWidth * 1; // * devicePixelRatio
canvas.height = window.innerHeight * 1;
// for retina: let dpr = window.devicePixelRatio; canvas.width = innerWidth*dpr; etc, ctx.scale(dpr,dpr);
To keep simple, no dpr first.
}
window.addEvent resize event.
Then variables:
let cx = -0.5, cy = 0;
let scale = 2.0; // initial scale, width = 4/scale or something.
Better: let zoom = 1; // zoom factor, higher more zoomed.
let minX, minY, max but compute on fly.
For mouse:
let dragging = false;
let lastX, lastY;
canvas.addEventListener('mousedown', e => {
dragging = true;
lastX = e.clientX;
lastY = e.clientY;
});
canvas.addEventListener('mousemove', e => {
if (dragging) {
let dx = (e.clientX - lastX) / canvas.width * rangeX;
let dy = (e.clientY - lastY) / canvas.height * rangeY;
cx -= dx; // direction: if drag right, cx decreases to move view left? Let's think .
// If I drag the mouse to the right, the image should move to the left, so center moves left, cx -= positive.
cy -= dy;
lastX = e.clientX;
lastY = e.clientY;
render();
}
});
For wheel:
canvas.addEventListener(' wheel', e => {
e.preventDefault();
let factor = e.deltaY > 0 ? 0.8 : 1.25; // zoom in if deltaY negative? e.deltaY positive for scroll down, zoom out.
zoom *= factor;
// adjust center to mouse pos
let rect = canvas.getBoundingClientRect();
let mx = e.clientX - rect.left;
let my = e.clientY - rect.top;
let mouseX = cx + (mx / canvas.width - 0.5) * rangeX; // wait define range.
Let's define properly.
Let the view width in complex plane be W = 3.5 / zoom; // initial zoom=1, W=3.5 covering -2 to 1.5 approx.
let W = 3.5 / zoom;
let H = W * canvas.height / canvas.width;
Then minRe = cx - W /2;
minIm = cy - H /2;
Then for screen to complex:
re = minRe + (px / width) * W;
im = minIm + (py / height) * H;
For pan:
if drag dx screen, deltaRe = dx / width * W;
cx -= delta (yes)
For wheel:
zoom *= factor;
W new = 3.5 / zoom;
H new = Wnew * aspect
Then to keep mouse fixed:
mouseRe = minRe + (mx / width) * W
Then new minRe = mouseRe - (mx / width) * Wnew wait.
minRe_new = mouseRe - (mx / width) * Wnew
Yes, because mouseRe = minRe + (mx/width)*W , so minRe = mouseRe - (mx/width)*W
So same for new.
Yes./tmp/ws/index.html (7835 bytes)Successfully wrote 7835 bytes to /tmp/ws/index.html
thinking
The file has been written. I need to verify it exists and perhaps do a quick test, but since it's a web app, I can use bash to check it and maybe confirm the size or something. The instruction is to e...
{"command":"ls -la /tmp/ws/index.html && wc -c /tmp/ws/index.html"}-rw-r--r--. 1 node node 7839 Aug 1 20:16 /tmp/ws/index.html 7839 /tmp/ws/index.html
thinking
The file is written and exists. It's a single self-contained HTML file with embedded CSS and JS. It renders the Mandelbrot set using canvas pixel manipulation, has smooth coloring via HSV + escape tim...
{"command":"head -n 30 /tmp/ws/index.html && echo \"...\" && tail -n 5 /tmp/ws/index.html"}<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Mandelbrot</title> <style> * { margin: 0; padding: 0; box-sizing: border-box; } html, body { width: 100%; height: 100%; overflow: hidden; background: #000; font-family: system-ui, -apple-system, sans-serif; } canvas { display: block; cursor: grab; touch-action: none; } #info { position: absolute; top: 12px; left: 12px; background: rgba(0, 0, 0, 0.65); color: #fff; padding: 8px 14px; border-radius: 6px; font-size: 12px; line-height: 1.4; pointer-events: none; ... init(); </script> </body> </html>
thinking
The index.html file has been created successfully as a single self-contained file. It includes:
Done. Created `/tmp/ws/index.html` — a fully self-contained single-file Mandelbrot explorer. **Features:** - Smooth gradient coloring via continuous iteration count (log-smoothed) - Full-screen canvas, adaptive max iterations with zoom - Click + drag to pan - Mouse wheel to zoom (centered under cursor) - Double-click to reset view - Keyboard: arrows to pan, +/- to zoom, R to reset No external dependencies or network access. Open in a browser to use.
TAKE IT TO CODE
A single self-contained HTML file — copy it and open in any browser, or reuse the prompt with your own pi-agent run.
RUN
EVALUATION
Mandelbrot set with smooth gradient coloring; drag pans and wheel zooms correctly, click/keys have no effect as expected.
Vision grade · anthropic/claude-sonnet-5
MEASUREMENTS
Raw readings from the capture, not a verdict — the grade above is the only judgement. Percentages are how much of the screen changed; the measure under-reports sparse motion on a dark background.