Gradient Text Hue Shift

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);

initDemoShell({ title: 'Gradient Text with Scroll Hue Shift', category: 'scroll', tech: ['gsap', 'scrolltrigger', 'css-variables'] });

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');

// Intro animation
if (!reduced) {
  gsap.set('.hero .eyebrow', { opacity: 0, y: 20 });
  gsap.set('.hero .gradient-text', { opacity: 0, y: 40 });
  gsap.set('.hero .subtitle', { opacity: 0, y: 25 });

  gsap.timeline({ defaults: { ease: 'expo.out' } })
    .to('.hero .eyebrow', { opacity: 1, y: 0, duration: 0.7, delay: 0.3 })
    .to('.hero .gradient-text', { opacity: 1, y: 0, duration: 0.9 }, '-=0.4')
    .to('.hero .subtitle', { opacity: 1, y: 0, duration: 0.7 }, '-=0.5');
}

// Hero gradient animation — synced to overall page scroll
if (!reduced) {
  gsap.to(document.documentElement, {
    '--hue-hero': 360,
    duration: 1,
    ease: 'none',
    scrollTrigger: {
      trigger: document.body,
      start: 'top top',
      end: 'bottom bottom',
      scrub: 0.8,
      onUpdate: (self) => {
        // Optional: update opacity based on progress
        const progress = self.progress;
        document.documentElement.style.setProperty('--hue-saturation', `${80 + progress * 20}%`);
      },
    },
  });
}

// Section-specific gradient animations
const gradientTexts = document.querySelectorAll('.gradient-text');
gradientTexts.forEach((el, index) => {
  if (el.closest('.hero')) return; // Skip hero, already animated

  // Initial state
  gsap.set(el, { opacity: 0, y: 30 });

  // Entrance animation
  gsap.to(el, {
    opacity: 1,
    y: 0,
    duration: 0.8,
    ease: 'expo.out',
    scrollTrigger: {
      trigger: el,
      start: 'top 75%',
      toggleActions: 'play none none reverse',
    },
  });

  // Section-specific hue shift
  if (!reduced) {
    const startHue = (index * 60) % 360;
    const endHue = (startHue + 120) % 360;

    gsap.to(el, {
      '--hue': endHue,
      duration: 1.2,
      ease: 'sine.inOut',
      scrollTrigger: {
        trigger: el,
        start: 'top 80%',
        end: 'bottom 20%',
        scrub: 1,
      },
    });

    gsap.set(el, { '--hue': startHue });
  }
});

// Stagger text content reveals
document.querySelectorAll('.spacer p, .spacer h2, .spacer ul, .showcase-1 p, .showcase-2 p, .showcase-3 p').forEach((el) => {
  if (!reduced) {
    gsap.set(el, { opacity: 0, y: 20 });
    gsap.to(el, {
      opacity: 1,
      y: 0,
      duration: 0.6,
      ease: 'expo.out',
      scrollTrigger: {
        trigger: el,
        start: 'top 75%',
        toggleActions: 'play none none reverse',
      },
    });
  }
});

// List items stagger
document.querySelectorAll('.spacer ul li').forEach((li, i) => {
  if (!reduced) {
    gsap.set(li, { opacity: 0, x: -20 });
    gsap.to(li, {
      opacity: 1,
      x: 0,
      duration: 0.6,
      ease: 'expo.out',
      delay: 0.05 * i,
      scrollTrigger: {
        trigger: li,
        start: 'top 75%',
        toggleActions: 'play none none reverse',
      },
    });
  }
});

// Code and ol elements
document.querySelectorAll('.spacer ol, .spacer code, .showcase-1 code').forEach((el) => {
  if (!reduced) {
    gsap.set(el, { opacity: 0, y: 15 });
    gsap.to(el, {
      opacity: 1,
      y: 0,
      duration: 0.6,
      ease: 'expo.out',
      scrollTrigger: {
        trigger: el,
        start: 'top 75%',
        toggleActions: 'play none none reverse',
      },
    });
  }
});

// Motion preference listener
window.addEventListener('motion-preference', (e) => {
  if (e.detail.reduced) {
    gsap.globalTimeline.paused(true);
  } else {
    gsap.globalTimeline.paused(false);
  }
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Gradient Text with Scroll Hue Shift — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
    <script type="importmap">{"imports":{"gsap":"/vendor/gsap/index.js","gsap/ScrollTrigger":"/vendor/gsap/ScrollTrigger.js","gsap/SplitText":"/vendor/gsap/SplitText.js","gsap/Flip":"/vendor/gsap/Flip.js","gsap/ScrambleTextPlugin":"/vendor/gsap/ScrambleTextPlugin.js","gsap/TextPlugin":"/vendor/gsap/TextPlugin.js","gsap/all":"/vendor/gsap/all.js","gsap/":"/vendor/gsap/","lenis":"/vendor/lenis/dist/lenis.mjs","three":"/vendor/three/build/three.module.js","three/addons/":"/vendor/three/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>
  <section class="hero">
    <div class="hero-content">
      <span class="eyebrow">Demo 37</span>
      <h1 class="gradient-text">Gradient Text Hue Shift</h1>
      <p class="subtitle">Text with animated gradient background that shifts hue and saturation as you scroll down the page. Pure CSS + GSAP ScrollTrigger.</p>
    </div>
  </section>

  <section class="spacer">
    <div class="content">
      <h2>How It Works</h2>
      <p>This effect uses CSS Custom Properties (CSS variables) to dynamically control the hue, saturation, and lightness of a gradient background applied to text.</p>
      <p>As the user scrolls, GSAP ScrollTrigger updates the CSS variables in real-time, creating a smooth color shift that feels organic and modern.</p>
    </div>
  </section>

  <section class="showcase-1">
    <div class="content">
      <h2 class="gradient-text">The Technique</h2>
      <p>A heading element uses <code>background: linear-gradient(...)</code> with CSS variables for hue rotation. Each section has its own hue range.</p>
      <p>The effect is simple but impactful: as you scroll past, the text color smoothly transitions through the color spectrum.</p>
    </div>
  </section>

  <section class="spacer">
    <div class="content">
      <h2>Perfect For</h2>
      <ul>
        <li><strong>Hero sections:</strong> Draw attention with color-shifting headlines</li>
        <li><strong>Section headers:</strong> Visual rhythm and engagement</li>
        <li><strong>Feature callouts:</strong> Highlight key messages</li>
        <li><strong>Portfolio pages:</strong> Modern, eye-catching typography</li>
        <li><strong>Marketing sites:</strong> Brand color integration and movement</li>
      </ul>
    </div>
  </section>

  <section class="showcase-2">
    <div class="content">
      <h2 class="gradient-text">Advanced Variations</h2>
      <p>You can layer multiple hue shifts, adjust saturation for desaturation on scroll, or synchronize the shift with other animations on the page.</p>
      <p>The gradient direction can also be linked to scroll velocity for even more dynamism.</p>
    </div>
  </section>

  <section class="spacer">
    <div class="content">
      <h2>Implementation</h2>
      <ol>
        <li>Define CSS variables for hue: <code>--hue: 0deg</code></li>
        <li>Apply gradient to text: <code>background: linear-gradient(to right, hsl(var(--hue), 100%, 50%), ...)</code></li>
        <li>Use <code>background-clip: text</code> to show only the gradient on text</li>
        <li>Update <code>--hue</code> with ScrollTrigger's <code>onUpdate</code> callback</li>
        <li>Wrap in <code>prefers-reduced-motion</code> check for accessibility</li>
      </ol>
    </div>
  </section>

  <section class="showcase-3">
    <div class="content">
      <h2 class="gradient-text">Responsive & Accessible</h2>
      <p>The effect gracefully degrades on browsers without gradient text support. When <code>prefers-reduced-motion</code> is enabled, the gradient is static or removed entirely.</p>
    </div>
  </section>

  <section class="final-section">
    <div class="content">
      <p style="text-align: center; color: var(--muted);">Scroll back to the top to see the hero gradient shift again.</p>
      <a href="/" class="btn-back">Back to Showcase</a>
    </div>
  </section>

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