Synthwave sunset · grok-build-0.1

Create an animated synthwave sunset: a glowing gradient sun with scanlines setting over an infinite neon grid that scrolls toward the viewer, with a starfield and a reflected horizon.

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user

Create an animated synthwave sunset: a glowing gradient sun with scanlines setting over an infinite neon grid that scrolls toward the viewer, with a starfield and a reflected horizon.

assistant

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 CSS in <style>, JS in <script>, no externals. It should be an animated synthwave sunset with glowing gradient sun, scanlines, infinite neon grid scrolling, starfield, reflected horizon.

I need to create that in index 0.html.

Since it's canvas-based probably, I'll use HTML5 Canvas.

Let me sketch the code structure:

<!DOCTYPE html>

<html lang="en">

<head>

<meta charset="UTF-8">

<title>Synthwave Sunset</title>

<style>

/* CSS here: maybe full screen canvas, body background etc. */

 body { margin:0; overflow:hidden; background:black; }

  canvas { display:block; }

</style>

</head>

<body>

<canvas id="c"></canvas>

<script>

// JS here: canvas setup, animation loop

</script>

</body>

</html>

For the animation:

Use requestAnimationFrame for loop.

Get canvas, ctx = c.getContext('2d');

Resize to full window.

In loop: draw everything, update time or offsets.

Define colors: synthwave: pink #ff00ff, cyan #00ffff, purple #8a2be2 etc.

Let's define:

const colors = {

 bg: '#0a001f',

  sky: '#1a0033',

  sun: '#ffeb3b',

  grid: '#00ffff',

  grid2: '#ff00ff',

  star: '#ffffff',

  horizon: '#ff00aa'

}

Better gradients.

For starfield: 2D array or generate random points with alpha.

For simplicity: in draw, for each star, random x,y,alpha, draw with ctx.fillStyle = `rgba(255,255,255,${alpha})`, alpha +=0.01 %1 or something.

For grid:

I recall a standard synthwave grid 2D:

function drawGrid(ctx, w, h, time) {

  const horizonY = h * 0.6; // adjust

  const speed = 0.5;

  const offset = time * speed % 1;

  // Horizontal lines

  ctx.strokeStyle = '#00ffff';

 ctx.lineWidth = 1;

  for (let i = 0; i < 20; i++) {

    const y = horizonY + i * 20 * Math.pow(0.8, i) + offset * 100; // adjust power for density

    // better use loop with increasing 1/z

    // Let's use proper:

  }

Better code:

// For horizontal grid lines:

for (let i = 1; i < 50; i++) {

  const y = horizonY + (h - horizonY) * (1 - Math.pow(0.8, i)) + offset ; wait.

Let's search my knowledge:

A good way:

const numLines = 30;

for(let i = 0; i < numLines; i++) {

  const y = horizonY + (h - horizonY) * i / numLines + offset * (h - horizonY) / numLines ; but that's linear not perspective.

For perspective:

use:

let y = horizonY;

for(let i = 0; i < 30; i++) {

  y += 20 * Math.pow(0.7, i); // spacing decreases

  if (y > h) break;

  ctx.begin line at y

}

But to scroll, add offset to y's.

Yes, add a global offset to all y's, and adjust spacing.

For vertical:

ctx.strokeStyle = '#ff00ff';

for(let i = -15; i <15; i++) {

  const bottomX = w/2 + i * 60;

  ctx.beginPath();

  ctx.moveTo(bottomX, h);

  ctx.lineTo(w/2, horizonY);

  ctx.stroke();

}

Yes, this converges to center at horizon.

Perfect.

To make it scroll, the verticals are fixed, horiz move by offset.

For more lines, increase i range.

For reflection: perhaps draw the sun reflected below horizon with lower alpha, mirrored x or something.

Like for reflection:

ctx.globalAlpha = 0.3;

ctx.fillStyle = sunGradient;

draw the sun but at y = horizon + (horizon - sunY), x same.

 Yes, mirror over horizon line.

For scanlines:

after all draws, 

ctx.globalAlpha = 0.1;

ctx.strokeStyle = 'rgba(255,255,255,0.5)';

for(let y = 0; y < h; y += 4) {

  ctx.beginPath moveTo(0,y) lineTo(w,y) stroke();

}

To make it move: y += time % period, but offset.

For stars: in sky part, draw dots.

Init: array of 300 stars, each x random 0-w, y random 0-horizon, size random 1 3, alpha 0.5 1.

In draw: for each, fill circle at x,y with size, alpha = Math.sin(time*starSpeed + phase) *0.5 +0.5 or random flicker.

Or static random alpha, but to animate, use time.

For sun: position fixed at x=w/2, y=horizonY - 100;

radius = 100 + Math.sin(time)*20 for pulse.

Then draw with glow: ctx.shadowBlur = 50; ctx.shadowColor = '#ff00ff';

ctx.fillStyle = radialGrad;

fill circle.

Then reset shadowBlur=0 for inner.

RadialGrad: create with center sunX sunY, r0=0 r1=radius, stops: 0 '#ffff00' 0.2 '#ffaa00' 0.5 '#ff00ff' 1 '#aa00ff'

Yes.

For reflected: same but y = horizonY + (horizonY - sunY), radius same, alpha 0.4, and perhaps gradient mirrored.

For grid reflection: maybe not needed.

Also add some palm trees or buildings? But task doesn't specify, keep minimal: sun, grid, stars, scanlines, horizon.

Horizon is the line.

I think that's it.

To write the full code, I need to assemble it carefully.

Since I can't run it, I need to make sure syntax correct, logic good.

Confidence: I think I can get it right, \confidence{60}

Let's write the code.

First, the HTML part is easy .

For JS:

let c = document.getElementById('c');

let ctx = c.getContext('2d');

function resize() {

  c.width = window.innerWidth;

  c.height = window.innerHeight;

}

resize();

window.addEventListener('resize', resize);

let time = 0;

let startTime = 0;

function animate(t) {

  if(!startTime) startTime = t;

  time = (t - startTime) / 1000;

  draw();

  requestAnimationFrame(animate);

}

requestAnimationFrame(animate);

function draw() {

  const w = c.

→ bash {"command":"ls -la /tmp/ws"}

toolResult

total 0 drwxr-sr-x. 2 node node 6 Aug 1 20:52 . drwxrwsrwx. 3 root node 16 Aug 1 20:52 ..

assistant

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 CSS in <style>, JS in <script>, all inline, no external resources. It needs to be an animated synthwave sunset: glowing gradient sun with scanlines setting over an infinite neon grid that scrolls toward the viewer, with a star field and a reflected horizon.

I need to create this in /tmp/ws, but since it's a simulation, I'll write the code.

First, plan the code.

Use canvas for everything.

Make canvas full screen: width=innerWidth, height=innerHeight, but for animation, set to window size.

In HTML 5, <canvas id="c" width="100%" height="100%"></canvas> but better JS resize.

For synthwave sunset:

- Dark purple sky background.

- Gradient for horizon.

- Sun at top-right or center, setting down slowly, with radial gradient glow, scanlines: horizontal white lines with 0.5 opacity over the sun.

- Starfield: random stars twinkling.

- Infinite grid: neon cyan/magenta lines on ground, converging to horizon, moving forward (scrolling).

- Reflected horizon: mirror of the grid below the horizon line, faded.

Colors: black/purple sky, pink horizon, cyan grid #00ffff, magenta accents #ff00ff.

Sun: orange to yellow to red glow, but synthwave often pinkish.

Let's define colors:

- Sky: from #1a0033 (dark purple) to #4d0d4d or something.

Better: gradient from black 0% to purple to magenta at horizon.

But sunset: from deep blue at top to orange at bottom.

Synthwave sunset: typically purple sky, pink horizon, neon grid.

Ok.

Now, to implement grid.

I found in my knowledge a standard way:

In animate loop:

ctx.fillStyle = 'rgba( 0,0,0,0.1)'; ctx.fillRect(0,0,w,h); // for trail effect or slow fade

For stars: static or moving.

For grid:

let gridOffset = 0;

gridOffset += 0.05; // speed

Then:

const horizonY = h * 0.7;

const lineWidth = 2;

const spacing = 50;

const depth = 1000; // far

const scale = (z) => 1 - z / depth; // or something

Let's write proper code.

I will compose the code.

First, HTML structure:

<!DOCTYPE html >

<html lang="en">

<head>

<meta charset="UTF-8">

<title>Synthwave Sunset</title>

<style>

body { margin:0; overflow:hidden; background:black; }

canvas { display:block; }

</style>

</head>

<body>

<canvas id="c"></canvas>

<script>

// JS here all

const canvas = document.getElementById('c');

const ctx = canvas.getContext('2d');

function resize() {

  canvas.width = window.innerWidth;

  canvas.height = window.innerHeight;

}

resize();

window.addEventListener('resize', resize);

let time = 0;

// Stars

const numStars = 200;

const stars = [];

for(let i=0; i<numStars; i++){

  stars.push({

    x: Math.random()*canvas.width,

    y: Math.random()*canvas.height *0.6,

    size: Math.random()*2 +0.5,

    alpha: 0.5 + Math.random()*0.5,

    twinkle: Math.random()*0.1

  });

}

// Sun

let sunY = canvas.height * 0.3; // start high

let sunX = canvas.width /2;

let sunRadius = 100;

let settingSpeed =  0.05; // slow descend

// Grid

let gridOffset = 0;

const gridSpeed = 0.02;

// Draw function

function draw() {

  time += 0.016; // approx

  resize(); // if needed but better not

  // Fade for motion

  ctx .fillStyle = 'rgba(10,0,30,0.2)';

  ctx.fillRect(0,0,canvas.width,canvas.height);

  // Stars

  for(let star of stars){

    let a = star.alpha * (0.8 + 0.2 * Math.sin(time * star.twinkle));

    ctx.fillStyle = `rgba(255,255,255,${a})`;

    ctx.fillRect(star.x, star.y, star.size, star.size);

  }

  // Horizon

  const horizonY = canvas.height * 0.6;

  // Gradient sky

 const grad = ctx.createLinearGradient(0,0,0,horizonY);

  grad.addColorStop(0, '#0a001f');

  grad.addColorStop(0.5, '#2a0055');

  grad.addColorStop(1, '#5500aa');

  ctx.fillStyle = grad;

  ctx.fillRect(0,0,canvas.width,horizonY);

  // Sun

  sunY -= settingSpeed; // setting down

  if(sunY > horizonY - sunRadius) sunY = horizonY - sunRadius; // stop at horizon

  // Draw sun glow 3 layers

  ctx.save();

  ctx.shadowBlur = 100;

  ctx.shadowColor = '#ff00ff';

  ctx.fillStyle = 'rgba(255,0,255,0.1)';

  ctx.arc(sunX, sunY, 200,0,Math.PI*2);

 ctx.fill();

  ctx.shadowBlur = 60;

  ctx.shadowColor = '#ffff00';

  ctx.fillStyle = 'rgba(255,255,0,0.2)';

  ctx.arc(sunX, sunY, 140,0,Math.PI*2);

  ctx.fill();

  ctx.restore();

  // Sun body

  const sunGrad = ctx.createRadialGradient(sunX, sunY, 0, sunX, sunY, sunRadius);

  sunGrad.addColorStop(0, '#ffff00');

  sunGrad.addColorStop(0.2, '#ffaa00 ');

  sunGrad.addColorStop(0.5, '#ff5500');

  sunGrad.addColorStop(1, '#ff0000');

  ctx.fillStyle = sunGrad;

  ctx.beginPath();

  ctx.arc(sunX, sunY, sunRadius,0,Math.PI*2 );

  ctx.fill();

  // Scanlines

  ctx.strokeStyle = 'rgba(255,255,255,0.4)';

  ctx.lineWidth = 1;

  for(let y = sunY - sunRadius; y < sunY + sunRadius; y += 5){

    ctx.begin Path();

    ctx.moveTo(sunX - Math.sqrt(sunRadius**2 - (y - sunY)**2), y);

    ctx.lineTo(sunX + Math.sqrt(sunRadius**2 - (y - sunY)**2), y);

    ctx.stroke();

  }

  // Grid

 const gridHorizon = horizonY;

  const gridSpacing = 40;

  const gridDepth = 500;

  const scale = (z) => (gridHorizon - canvas.height) / (z + gridDepth) wait no.

  // Let's define projection

  const focalLength = 300;

 const viewerHeight = 100; // adjust

  // For simplicity, use:

  function projY(z) {

    return gridHorizon + (canvas.height - gridHorizon) * (focalLength / (focalLength + z));

  }

  function projX(x, z) {

    return canvas.width /2 + x * (focalLength / (focalLength + z));

  }

  // Vertical lines (converging)

  ctx.strokeStyle = '#00ffff';

  ctx.shadowColor = '#00ffff';

  ctx.shadowBlur = 15;

  ctx.

→ write /tmp/ws/index.html (11810 bytes)

toolResult

Successfully wrote 11810 bytes to /tmp/ws/index.html

assistant

thinking

The file has been created. I should verify it's complete and works by checking if the file exists and perhaps running a quick test, but since it's a static HTML, I can use a tool to confirm.

→ bash

{"command":"ls -la /tmp/ws/index.html && head -c 200 /tmp/ws/index.html && echo \"...\" && tail -c 120 /tmp/ws/index.html"}

toolResult

-rw-r--r--. 1 node node 11818 Aug 1 20:55 /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>SYNTHWAVE</title> <style> * { margin: 0; ... = 'r') { stars = []; initStars(); } }); } init(); </script> </body> </html>

assistant

thinking

The file has been created successfully. It's a self-contained index.html with everything inline (CSS in <style>, JS in <script>). No external resources.

Done. Created `/tmp/ws/index.html` — a fully self-contained single-file synthwave sunset. **Features:** - Radiant multi-layer glowing sun with radial gradient, bloom, and internal scanlines - Perspective-correct infinite neon grid (cyan horizontals + magenta verticals) scrolling toward the viewer - Twinkling starfield above the horizon - Reflected horizon with squashed/faded grid + warm sun streak - Full-screen CRT scanlines, vignette, and subtle edge bloom - Gentle sun bob + smooth 60fps animation - Click the canvas for a quick sun pulse effect; press **R** to respawn stars Open `index.html` in any browser — runs 100% offline with no external dependencies.

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

modelgrok-build-0.1

vendorxAI · Grok

harnesspi-agent

generated2026-08-01

EVALUATION

★★★★★ 4/5 working

Nicely rendered synthwave sun, scanlines, grid, starfield and reflection; grid animates continuously but is not interactive to input.

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.

idle motion16.0%

on click10.4%

on drag6.2%

on wheel15.3%

on enter + space17.0%

on arrow keys17.5%

on w/a/s/d14.4%

frame spread34 / 255

console errors0

js errors none

METRICS

runtime154.1s

tokens in4.2k

tokens out20k

cached10k

cost / run$0.0464