Noise & Grain Overlay

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg: #0a0c14;
  --text: #f0f4fb;
  --muted: #8a95a8;
  --accent: #86e8ff;
  --border: #263249;
}

.hidden-svg {
  position: absolute;
  width: 0;
  height: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: "Inter", "SF Pro Display", system-ui, sans-serif;
  min-height: 100vh;
}

/* Overlays */
.overlay {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 100;
}

.noise-overlay {
  filter: url(#noise-filter);
  opacity: 0.06;
  mix-blend-mode: overlay;
  animation: noise-shift 0.5s steps(4) infinite;
}

@keyframes noise-shift {
  0% {
    transform: translate(0, 0);
  }
  25% {
    transform: translate(-2px, 1px);
  }
  50% {
    transform: translate(1px, -1px);
  }
  75% {
    transform: translate(-1px, 2px);
  }
}

.grain-canvas-overlay {
  opacity: 0.08;
  mix-blend-mode: overlay;
}
.grain-canvas-overlay canvas {
  width: 100%;
  height: 100%;
  image-rendering: pixelated;
}

.scanlines-overlay {
  background: repeating-linear-gradient(
    0deg,
    transparent,
    transparent 2px,
    rgba(0, 0, 0, 0.15) 2px,
    rgba(0, 0, 0, 0.15) 4px
  );
  opacity: 0; /* off by default */
}

.vignette-overlay {
  background: radial-gradient(ellipse at center, transparent 50%, rgba(0, 0, 0, 0.6) 100%);
  opacity: 1;
}

.overlay.off {
  opacity: 0 !important;
}

.reduced-motion .noise-overlay {
  animation: none;
}

/* Page */
.page {
  position: relative;
  z-index: 2;
  max-width: 800px;
  margin: 0 auto;
  padding: 5rem 2rem 4rem;
}

.header {
  text-align: center;
  margin-bottom: 2rem;
}
.eyebrow {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--accent);
  margin-bottom: 1rem;
}
h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}
.subtitle {
  font-size: clamp(0.9rem, 2vw, 1.05rem);
  color: var(--muted);
  max-width: 480px;
  margin: 0.75rem auto 0;
  line-height: 1.6;
}

/* Controls */
.controls {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-bottom: 2.5rem;
}
.toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.9rem;
  border-radius: 8px;
  background: rgba(134, 232, 255, 0.05);
  border: 1px solid var(--border);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--muted);
  cursor: pointer;
  transition: border-color 0.2s;
}
.toggle:has(input:checked) {
  border-color: var(--accent);
  color: var(--accent);
}
.toggle input {
  accent-color: var(--accent);
}

/* Sample content */
.sample-hero {
  aspect-ratio: 16 / 7;
  border-radius: 18px;
  margin-bottom: 1rem;
  background: linear-gradient(
    135deg,
    hsl(var(--hue, 200) 45% 12%),
    hsl(var(--hue, 200) 60% 22%),
    hsl(calc(var(--hue, 200) +40) 50% 16%)
  );
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2rem;
}
.sample-hero h2 {
  font-size: clamp(1.5rem, 3vw, 2.2rem);
  font-weight: 700;
  margin-bottom: 0.5rem;
}
.sample-hero p {
  font-size: 0.9rem;
  color: rgba(255, 255, 255, 0.6);
}

.sample-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-bottom: 2rem;
}
.sample-card {
  aspect-ratio: 1.2;
  border-radius: 14px;
  background: linear-gradient(135deg, hsl(var(--hue, 200) 40% 12%), hsl(var(--hue, 200) 55% 20%));
  border: 1px solid hsl(var(--hue, 200) 30% 20%);
  display: flex;
  align-items: center;
  justify-content: center;
  font: 600 0.85rem / 1 "Inter", system-ui, sans-serif;
  color: hsl(var(--hue, 200) 60% 75%);
}

.btn-back {
  display: inline-block;
  padding: 0.7rem 2rem;
  border-radius: 999px;
  border: 1px solid rgba(134, 232, 255, 0.3);
  color: var(--accent);
  text-decoration: none;
  font: 600 0.85rem / 1 "Inter", system-ui, sans-serif;
  transition: all 0.25s;
}
.btn-back:hover {
  background: rgba(134, 232, 255, 0.08);
  border-color: var(--accent);
}

@media (max-width: 640px) {
  .sample-row {
    grid-template-columns: 1fr;
  }
  .page {
    padding: 3rem 1rem 3rem;
  }
}

if (!window.MotionPreference) {
  const __mql = window.matchMedia("(prefers-reduced-motion: reduce)");
  const __listeners = new Set();

  const MotionPreference = {
    prefersReducedMotion() {
      return __mql.matches;
    },
    setOverride(value) {
      const reduced = Boolean(value);
      document.documentElement.classList.toggle("reduced-motion", reduced);
      window.dispatchEvent(new CustomEvent("motion-preference", { detail: { reduced } }));
      for (const listener of __listeners) {
        try {
          listener({ reduced, override: reduced, systemReduced: __mql.matches });
        } catch {}
      }
    },
    onChange(listener) {
      __listeners.add(listener);
      try {
        listener({
          reduced: __mql.matches,
          override: null,
          systemReduced: __mql.matches,
        });
      } catch {}
      return () => __listeners.delete(listener);
    },
    getState() {
      return { reduced: __mql.matches, override: null, systemReduced: __mql.matches };
    },
  };

  window.MotionPreference = MotionPreference;
}

function prefersReducedMotion() {
  return window.MotionPreference.prefersReducedMotion();
}

function initDemoShell() {
  // No-op shim in imported standalone snippets.
}

initDemoShell({
  title: "Noise & Grain Overlay",
  category: "css-canvas",
  tech: ["svg-filter", "canvas", "css"],
});

let reduced = prefersReducedMotion();
if (reduced) document.documentElement.classList.add("reduced-motion");

// Refs
const noiseOverlay = document.getElementById("noise-overlay");
const scanlinesOverlay = document.getElementById("scanlines-overlay");
const vignetteOverlay = document.querySelector(".vignette-overlay");
const grainCanvas = document.getElementById("grain-canvas");
const grainCtx = grainCanvas.getContext("2d");

// Canvas grain — tiny resolution, scaled up with pixelated rendering
const GRAIN_SIZE = 128;
grainCanvas.width = GRAIN_SIZE;
grainCanvas.height = GRAIN_SIZE;

let grainRAF;
let grainFrame = 0;

function renderGrain() {
  grainFrame++;
  // Only update every 3 frames for flickering effect
  if (grainFrame % 3 === 0) {
    const imageData = grainCtx.createImageData(GRAIN_SIZE, GRAIN_SIZE);
    const data = imageData.data;
    for (let i = 0; i < data.length; i += 4) {
      const v = Math.random() * 255;
      data[i] = v; // R
      data[i + 1] = v; // G
      data[i + 2] = v; // B
      data[i + 3] = 255; // A
    }
    grainCtx.putImageData(imageData, 0, 0);
  }
  grainRAF = requestAnimationFrame(renderGrain);
}

if (!reduced) {
  renderGrain();
}

// Toggle controls
function setupToggle(id, overlay) {
  const checkbox = document.getElementById(id);
  const update = () => overlay.classList.toggle("off", !checkbox.checked);
  checkbox.addEventListener("change", update);
  update();
}

setupToggle("tog-noise", noiseOverlay);
setupToggle("tog-grain", grainCanvas.parentElement);
setupToggle("tog-scanlines", scanlinesOverlay);
setupToggle("tog-vignette", vignetteOverlay);

// Motion preference
window.addEventListener("motion-preference", (e) => {
  reduced = e.detail.reduced;
  document.documentElement.classList.toggle("reduced-motion", reduced);
  if (reduced) {
    cancelAnimationFrame(grainRAF);
  } else {
    renderGrain();
  }
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Noise &amp; Grain Overlay — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
  </head>
<body>
  <!-- SVG noise filter (hidden) -->
  <svg class="hidden-svg">
    <filter id="noise-filter">
      <feTurbulence type="fractalNoise" baseFrequency="0.65" numOctaves="3" stitchTiles="stitch" id="turbulence"/>
      <feColorMatrix type="saturate" values="0"/>
    </filter>
  </svg>

  <!-- Overlays -->
  <div class="overlay noise-overlay" id="noise-overlay"></div>
  <div class="overlay grain-canvas-overlay"><canvas id="grain-canvas" aria-hidden="true"></canvas></div>
  <div class="overlay scanlines-overlay" id="scanlines-overlay"></div>
  <div class="overlay vignette-overlay"></div>

  <!-- Content -->
  <main class="page">
    <header class="header">
      <span class="eyebrow">Demo 18</span>
      <h1>Noise &amp; Grain</h1>
      <p class="subtitle">Multiple overlay techniques composited on top of content: SVG noise filter, canvas grain, scanlines, and vignette.</p>
    </header>

    <div class="controls">
      <label class="toggle"><input type="checkbox" id="tog-noise" checked><span>SVG Noise</span></label>
      <label class="toggle"><input type="checkbox" id="tog-grain" checked><span>Canvas Grain</span></label>
      <label class="toggle"><input type="checkbox" id="tog-scanlines"><span>Scanlines</span></label>
      <label class="toggle"><input type="checkbox" id="tog-vignette" checked><span>Vignette</span></label>
    </div>

    <div class="sample-content">
      <div class="sample-hero" style="--hue: 220;">
        <h2>Cinematic Texture</h2>
        <p>Film grain adds warmth and analog character to digital interfaces.</p>
      </div>
      <div class="sample-row">
        <div class="sample-card" style="--hue: 280;">Visual Depth</div>
        <div class="sample-card" style="--hue: 340;">Atmosphere</div>
        <div class="sample-card" style="--hue: 50;">Nostalgia</div>
      </div>
    </div>

    <a href="/" class="btn-back">Back to Showcase</a>
  </main>

  <script src="script.js"></script>
</body>
</html>