Horizontal Scroll Gallery

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

:root {
  --bg: #070a12;
  --text: #f0f4fb;
  --muted: #8a95a8;
  --accent: #86e8ff;
  --neon-purple: #ae52ff;
}

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

body {
  overflow-x: hidden;
}

/* ── Intro ── */
.intro {
  min-height: 80vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2rem;
}

.eyebrow {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--accent);
  margin-bottom: 1rem;
}

h1 {
  font-size: clamp(2.2rem, 6vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.05;
  background: linear-gradient(135deg, #fff, var(--accent), var(--neon-purple));
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.subtitle {
  font-size: clamp(0.9rem, 2vw, 1.1rem);
  color: var(--muted);
  max-width: 460px;
  margin-top: 0.75rem;
  line-height: 1.6;
}

.scroll-hint {
  margin-top: 2.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  color: var(--muted);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.scroll-arrow {
  width: 1px;
  height: 28px;
  background: linear-gradient(to bottom, var(--accent), transparent);
  animation: arrow-pulse 1.8s ease-in-out infinite;
}

@keyframes arrow-pulse {
  0%,
  100% {
    opacity: 0.3;
    transform: scaleY(0.6);
  }
  50% {
    opacity: 1;
    transform: scaleY(1);
  }
}

.reduced-motion .scroll-arrow {
  animation: none;
  opacity: 0.5;
}

/* ── Progress bar ── */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: rgba(255, 255, 255, 0.05);
  z-index: 100;
  opacity: 0;
  transition: opacity 0.3s;
}

.progress-bar.visible {
  opacity: 1;
}

.progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--neon-purple));
  transform-origin: left;
  will-change: width;
}

/* ── Horizontal section ── */
.horizontal-wrap {
  position: relative;
  overflow: hidden;
}

.horizontal-track {
  display: flex;
  width: max-content;
  will-change: transform;
}

/* ── Panels ── */
.panel {
  width: 80vw;
  max-width: 700px;
  height: 100vh;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
}

.panel-inner {
  background: linear-gradient(135deg, hsl(var(--hue, 200) 50% 10%), hsl(var(--hue, 200) 60% 16%));
  border: 1px solid hsl(var(--hue, 200) 40% 25%);
  border-radius: 20px;
  padding: 3rem;
  width: 100%;
  max-width: 550px;
  min-height: 380px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  will-change: transform, opacity;
  transition: box-shadow 0.4s ease;
}

.panel-inner:hover {
  box-shadow: 0 8px 48px hsla(var(--hue, 200), 60%, 30%, 0.15);
}

.panel-number {
  font-size: 4rem;
  font-weight: 700;
  color: hsla(var(--hue, 200), 60%, 60%, 0.15);
  line-height: 1;
  margin-bottom: 1rem;
}

.panel-inner h2 {
  font-size: clamp(2rem, 4vw, 3.2rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.05;
  color: hsl(var(--hue, 200) 70% 80%);
  margin-bottom: 1rem;
}

.panel-inner p {
  font-size: 1rem;
  color: var(--muted);
  line-height: 1.6;
  max-width: 380px;
}

/* ── Outro ── */
.outro {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2rem;
}

.outro h2 {
  font-size: clamp(1.8rem, 4vw, 3rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 1.5rem;
}

.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 ease;
}

.btn-back:hover {
  background: rgba(134, 232, 255, 0.08);
  border-color: var(--accent);
}

/* ── Reduced motion ── */
.reduced-motion .panel-inner {
  opacity: 1 !important;
  transform: none !important;
}

@media (max-width: 640px) {
  .panel {
    width: 90vw;
    padding: 1rem;
  }
  .panel-inner {
    padding: 2rem;
    min-height: 300px;
  }
}

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.
}

import gsap from "gsap";
import { ScrollTrigger } from "gsap/ScrollTrigger";
import Lenis from "lenis";

gsap.registerPlugin(ScrollTrigger);

// ── Demo shell ──
initDemoShell({
  title: "Horizontal Scroll Gallery",
  category: "scroll",
  tech: ["gsap", "lenis", "scrolltrigger"],
});

// ── Lenis ──
const lenis = new Lenis({ lerp: 0.1, smoothWheel: true });
lenis.on("scroll", ScrollTrigger.update);
gsap.ticker.add((time) => lenis.raf(time * 1000));
gsap.ticker.lagSmoothing(0);

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

window.addEventListener("motion-preference", (e) => {
  document.documentElement.classList.toggle("reduced-motion", e.detail.reduced);
  ScrollTrigger.refresh();
});

// ── Refs ──
const track = document.getElementById("horizontal-track");
const panels = gsap.utils.toArray(".panel");
const progressFill = document.getElementById("progress-fill");
const progressBar = document.querySelector(".progress-bar");

// ── Calculate total scroll distance ──
function getScrollWidth() {
  return track.scrollWidth - window.innerWidth;
}

// ── Horizontal scroll pin ──
const horizontalTween = gsap.to(track, {
  x: () => -getScrollWidth(),
  ease: "none",
  scrollTrigger: {
    trigger: ".horizontal-wrap",
    pin: true,
    scrub: 1,
    end: () => `+=${getScrollWidth()}`,
    invalidateOnRefresh: true,
    onUpdate: (self) => {
      // Update progress bar
      progressFill.style.width = `${self.progress * 100}%`;
    },
    onEnter: () => progressBar.classList.add("visible"),
    onLeave: () => progressBar.classList.remove("visible"),
    onEnterBack: () => progressBar.classList.add("visible"),
    onLeaveBack: () => progressBar.classList.remove("visible"),
  },
});

// ── Panel entrance animations ──
if (!reduced) {
  panels.forEach((panel) => {
    const inner = panel.querySelector(".panel-inner");

    gsap.set(inner, { opacity: 0.3, scale: 0.88 });

    gsap.to(inner, {
      opacity: 1,
      scale: 1,
      duration: 1,
      ease: "power2.out",
      scrollTrigger: {
        trigger: panel,
        containerAnimation: horizontalTween,
        start: "left 80%",
        end: "left 30%",
        scrub: 1,
      },
    });
  });
}

// ── Intro animations ──
if (!reduced) {
  const introTl = gsap.timeline({ defaults: { ease: "expo.out" } });

  gsap.set(".intro .eyebrow", { opacity: 0, y: 20 });
  gsap.set(".intro h1", { opacity: 0, y: 40 });
  gsap.set(".intro .subtitle", { opacity: 0, y: 25 });
  gsap.set(".intro .scroll-hint", { opacity: 0 });

  introTl
    .to(".intro .eyebrow", { opacity: 1, y: 0, duration: 0.7, delay: 0.3 })
    .to(".intro h1", { opacity: 1, y: 0, duration: 0.9 }, "-=0.4")
    .to(".intro .subtitle", { opacity: 1, y: 0, duration: 0.7 }, "-=0.5")
    .to(".intro .scroll-hint", { opacity: 1, duration: 0.5 }, "-=0.3");
}

// ── Outro reveal ──
if (!reduced) {
  gsap.set(".outro h2", { opacity: 0, y: 40 });
  gsap.set(".btn-back", { opacity: 0, y: 20 });

  gsap.to(".outro h2", {
    opacity: 1,
    y: 0,
    duration: 0.8,
    ease: "expo.out",
    scrollTrigger: { trigger: ".outro", start: "top 70%" },
  });

  gsap.to(".btn-back", {
    opacity: 1,
    y: 0,
    duration: 0.6,
    ease: "expo.out",
    scrollTrigger: { trigger: ".outro", start: "top 60%" },
  });
}

// ── Handle resize ──
window.addEventListener("resize", () => {
  ScrollTrigger.refresh();
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Horizontal Scroll Gallery — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
    <script type="importmap">{"imports":{"gsap":"https://esm.sh/gsap@3.13.0","gsap/ScrollTrigger":"https://esm.sh/gsap@3.13.0/ScrollTrigger","gsap/SplitText":"https://esm.sh/gsap@3.13.0/SplitText","gsap/Flip":"https://esm.sh/gsap@3.13.0/Flip","gsap/ScrambleTextPlugin":"https://esm.sh/gsap@3.13.0/ScrambleTextPlugin","gsap/TextPlugin":"https://esm.sh/gsap@3.13.0/TextPlugin","gsap/all":"https://esm.sh/gsap@3.13.0/all","gsap/":"https://esm.sh/gsap@3.13.0/","lenis":"https://esm.sh/lenis@1.1.13/dist/lenis.mjs","three":"https://esm.sh/three@0.171.0","three/addons/":"https://esm.sh/three@0.171.0/examples/jsm/"}}</script>
  <style>html.lenis,
html.lenis body {
  height: auto;
}

.lenis:not(.lenis-autoToggle).lenis-stopped {
  overflow: clip;
}

.lenis [data-lenis-prevent],
.lenis [data-lenis-prevent-wheel],
.lenis [data-lenis-prevent-touch] {
  overscroll-behavior: contain;
}

.lenis.lenis-smooth iframe {
  pointer-events: none;
}

.lenis.lenis-autoToggle {
  transition-property: overflow;
  transition-duration: 1ms;
  transition-behavior: allow-discrete;
}</style>
</head>
<body>
  <!-- Intro -->
  <section class="intro">
    <span class="eyebrow">Demo 02</span>
    <h1>Horizontal Scroll Gallery</h1>
    <p class="subtitle">Scroll down — the gallery scrolls sideways. Each panel reveals with scale and opacity transitions.</p>
    <div class="scroll-hint">
      <span>Scroll to explore</span>
      <div class="scroll-arrow"></div>
    </div>
  </section>

  <!-- Horizontal section -->
  <section class="horizontal-wrap">
    <div class="progress-bar"><div class="progress-fill" id="progress-fill"></div></div>
    <div class="horizontal-track" id="horizontal-track">

      <div class="panel" style="--hue: 200;">
        <div class="panel-inner">
          <span class="panel-number">01</span>
          <h2>Kinetic<br>Typography</h2>
          <p>Letters and words choreographed with scroll-driven timelines.</p>
        </div>
      </div>

      <div class="panel" style="--hue: 270;">
        <div class="panel-inner">
          <span class="panel-number">02</span>
          <h2>Particle<br>Systems</h2>
          <p>Thousands of elements forming organic, flowing structures.</p>
        </div>
      </div>

      <div class="panel" style="--hue: 330;">
        <div class="panel-inner">
          <span class="panel-number">03</span>
          <h2>Scroll<br>Choreography</h2>
          <p>Precisely timed sequences that unfold with the user's scroll.</p>
        </div>
      </div>

      <div class="panel" style="--hue: 45;">
        <div class="panel-inner">
          <span class="panel-number">04</span>
          <h2>Shader<br>Art</h2>
          <p>GPU-powered visuals creating mesmerizing real-time patterns.</p>
        </div>
      </div>

      <div class="panel" style="--hue: 160;">
        <div class="panel-inner">
          <span class="panel-number">05</span>
          <h2>3D<br>Environments</h2>
          <p>Immersive spaces built with WebGL and Three.js.</p>
        </div>
      </div>

      <div class="panel" style="--hue: 15;">
        <div class="panel-inner">
          <span class="panel-number">06</span>
          <h2>Magnetic<br>Interactions</h2>
          <p>Elements that attract and repel based on cursor proximity.</p>
        </div>
      </div>

    </div>
  </section>

  <!-- Outro -->
  <section class="outro">
    <h2>Gallery complete.</h2>
    <a href="/" class="btn-back">Back to Showcase</a>
  </section>

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