Image Gallery Transitions

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

:root {
  --bg: #070a12;
  --text: #f0f4fb;
  --muted: #8a95a8;
  --accent: #86e8ff;
  --border: #263249;
}

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

.header {
  text-align: center;
  padding: 5rem 2rem 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, 3rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}
.subtitle {
  font-size: clamp(0.9rem, 2vw, 1.05rem);
  color: var(--muted);
  max-width: 460px;
  margin: 0.75rem auto 0;
  line-height: 1.6;
}

/* Gallery */
.gallery {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem;
}

.hero-area {
  margin-bottom: 1.5rem;
}

.hero-image {
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: 18px;
  background: linear-gradient(
    135deg,
    hsl(var(--hue, 200) 50% 12%),
    hsl(var(--hue, 200) 65% 22%),
    hsl(calc(var(--hue, 200) + 50) 50% 18%)
  );
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.hero-number {
  font-size: 6rem;
  font-weight: 700;
  color: rgba(255, 255, 255, 0.06);
  line-height: 1;
}

.hero-label {
  font-size: 1.1rem;
  font-weight: 600;
  color: rgba(255, 255, 255, 0.7);
  margin-top: -0.5rem;
}

/* Thumbnails */
.thumb-strip {
  display: flex;
  gap: 0.6rem;
  overflow-x: auto;
  padding: 0.5rem 0 1.5rem;
  scroll-snap-type: x mandatory;
  -ms-overflow-style: none;
  scrollbar-width: none;
}
.thumb-strip::-webkit-scrollbar {
  display: none;
}

.thumb {
  flex-shrink: 0;
  width: 100px;
  height: 70px;
  border-radius: 10px;
  background: linear-gradient(135deg, hsl(var(--hue, 200) 40% 12%), hsl(var(--hue, 200) 55% 20%));
  border: 2px solid transparent;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font: 700 1.2rem / 1 "Inter", system-ui, sans-serif;
  color: rgba(255, 255, 255, 0.15);
  transition: border-color 0.25s, transform 0.25s;
  scroll-snap-align: center;
}
.thumb:hover {
  border-color: rgba(134, 232, 255, 0.3);
  transform: translateY(-2px);
}
.thumb.active {
  border-color: var(--accent);
  box-shadow: 0 0 16px rgba(134, 232, 255, 0.15);
}

/* View Transitions */
::view-transition-old(hero-img) {
  animation: hero-out 0.3s ease-in;
}
::view-transition-new(hero-img) {
  animation: hero-in 0.35s ease-out;
}

@keyframes hero-out {
  to {
    opacity: 0;
    transform: scale(0.96);
  }
}
@keyframes hero-in {
  from {
    opacity: 0;
    transform: scale(1.04);
  }
}

.footer {
  text-align: center;
  padding: 1.5rem 2rem 3rem;
}
.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) {
  .thumb {
    width: 80px;
    height: 56px;
  }
  .gallery {
    padding: 0 1rem;
  }
}

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: "Image Gallery Transitions",
  category: "transitions",
  tech: ["view-transitions-api", "crossfade"],
});

const supportsVT = typeof document.startViewTransition === "function";
const heroImage = document.getElementById("hero-image");
const heroNumber = document.getElementById("hero-number");
const heroLabel = document.getElementById("hero-label");
const thumbs = document.querySelectorAll(".thumb");

let currentIndex = 0;

function selectImage(index) {
  if (index === currentIndex) return;

  const thumb = document.querySelector(`.thumb[data-index="${index}"]`);
  if (!thumb) return;

  const hue = thumb.dataset.hue;
  const label = thumb.dataset.label;
  const num = String(index + 1).padStart(2, "0");

  const updateDOM = () => {
    heroImage.style.setProperty("--hue", hue);
    heroNumber.textContent = num;
    heroLabel.textContent = label;

    thumbs.forEach((t, i) => t.classList.toggle("active", i === index));
    currentIndex = index;
  };

  if (supportsVT && !prefersReducedMotion()) {
    document.startViewTransition(updateDOM);
  } else {
    updateDOM();
  }
}

// Click handlers
thumbs.forEach((thumb) => {
  thumb.addEventListener("click", () => {
    selectImage(parseInt(thumb.dataset.index, 10));
  });
});

// Keyboard navigation
document.addEventListener("keydown", (e) => {
  if (e.key === "ArrowRight") {
    selectImage(Math.min(currentIndex + 1, thumbs.length - 1));
  } else if (e.key === "ArrowLeft") {
    selectImage(Math.max(currentIndex - 1, 0));
  }
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Image Gallery Transitions — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
  </head>
<body>
  <header class="header">
    <span class="eyebrow">Demo 14</span>
    <h1>Image Gallery</h1>
    <p class="subtitle">Click a thumbnail to see a smooth crossfade with scale using View Transitions. The hero image morphs between selections.</p>
  </header>

  <main class="gallery">
    <div class="hero-area">
      <div class="hero-image" id="hero-image" style="view-transition-name: hero-img; --hue: 200;">
        <span class="hero-number" id="hero-number">01</span>
        <span class="hero-label" id="hero-label">Aurora Borealis</span>
      </div>
    </div>

    <div class="thumb-strip" id="thumb-strip">
      <button class="thumb active" data-index="0" data-hue="200" data-label="Aurora Borealis" style="--hue: 200;"><span>01</span></button>
      <button class="thumb" data-index="1" data-hue="270" data-label="Nebula Cloud" style="--hue: 270;"><span>02</span></button>
      <button class="thumb" data-index="2" data-hue="330" data-label="Sunset Gradient" style="--hue: 330;"><span>03</span></button>
      <button class="thumb" data-index="3" data-hue="45" data-label="Golden Hour" style="--hue: 45;"><span>04</span></button>
      <button class="thumb" data-index="4" data-hue="160" data-label="Deep Forest" style="--hue: 160;"><span>05</span></button>
      <button class="thumb" data-index="5" data-hue="15" data-label="Ember Glow" style="--hue: 15;"><span>06</span></button>
      <button class="thumb" data-index="6" data-hue="240" data-label="Midnight Sky" style="--hue: 240;"><span>07</span></button>
      <button class="thumb" data-index="7" data-hue="90" data-label="Spring Meadow" style="--hue: 90;"><span>08</span></button>
    </div>
  </main>

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

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