CodePen Embed - you can scroll.

<header>
      <h1 class="fluid">you can<br />scroll.</h1>
    </header>
    <main>
      <section class="content fluid">
        <h2><span aria-hidden="true">you can&nbsp;</span>
          <span class="sr-only">you can ship things.</span>
        </h2>
        <ul aria-hidden="true" style="--count: 22">
          <li style="--i: 0">design.</li>
          <li style="--i: 1">prototype.</li>
          <li style="--i: 2">solve.</li>
          <li style="--i: 3">build.</li>
          <li style="--i: 4">develop.</li>
          <li style="--i: 5">debug.</li>
          <li style="--i: 6">learn.</li>
          <li style="--i: 7">cook.</li>
          <li style="--i: 8">ship.</li>
          <li style="--i: 9">prompt.</li>
          <li style="--i: 10">collaborate.</li>
          <li style="--i: 11">create.</li>
          <li style="--i: 12">inspire.</li>
          <li style="--i: 13">follow.</li>
          <li style="--i: 14">innovate.</li>
          <li style="--i: 15">test.</li>
          <li style="--i: 16">optimize.</li>
          <li style="--i: 17">teach.</li>
          <li style="--i: 18">visualize.</li>
          <li style="--i: 19">transform.</li>
          <li style="--i: 20">scale.</li>
          <li style="--i: 21">do it.</li>
        </ul>
      </section>
      <section>
        <h2 class="fluid">fin.</h2>
      </section>
    </main>
    <footer>ʕ⊙ᴥ⊙ʔ jh3yy &copy; 2024</footer>
    <a
      class="bear-link"
      href="https://twitter.com/intent/follow?screen_name=jh3yy"
      target="_blank"
      rel="noreferrer noopener"
    >
      <svg
        class="w-9"
        viewBox="0 0 969 955"
        fill="none"
        xmlns="http://www.w3.org/2000/svg"
      >
        <circle
          cx="161.191"
          cy="320.191"
          r="133.191"
          stroke="currentColor"
          stroke-width="20"
        ></circle>
        <circle
          cx="806.809"
          cy="320.191"
          r="133.191"
          stroke="currentColor"
          stroke-width="20"
        ></circle>
        <circle
          cx="695.019"
          cy="587.733"
          r="31.4016"
          fill="currentColor"
        ></circle>
        <circle
          cx="272.981"
          cy="587.733"
          r="31.4016"
          fill="currentColor"
        ></circle>
        <path
          d="M564.388 712.083C564.388 743.994 526.035 779.911 483.372 779.911C440.709 779.911 402.356 743.994 402.356 712.083C402.356 680.173 440.709 664.353 483.372 664.353C526.035 664.353 564.388 680.173 564.388 712.083Z"
          fill="currentColor"
        ></path>
        <rect
          x="310.42"
          y="448.31"
          width="343.468"
          height="51.4986"
          fill="#FF1E1E"
        ></rect>
        <path
          fill-rule="evenodd"
          clip-rule="evenodd"
          d="M745.643 288.24C815.368 344.185 854.539 432.623 854.539 511.741H614.938V454.652C614.938 433.113 597.477 415.652 575.938 415.652H388.37C366.831 415.652 349.37 433.113 349.37 454.652V511.741L110.949 511.741C110.949 432.623 150.12 344.185 219.845 288.24C289.57 232.295 384.138 200.865 482.744 200.865C581.35 200.865 675.918 232.295 745.643 288.24Z"
          fill="currentColor"
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      </svg>
    </a>

@import url('https://fonts.googleapis.com/css2?family=Geist:wght@100..900&display=swap');
@import url('https://unpkg.com/normalize.css') layer(normalize);

@layer normalize, base, demo, stick, effect, srollbar, debug;

@layer debug {
  [data-debug='true'] li {
    outline: 0.05em dashed currentColor;
  }
  [data-debug='true'] :is(h2, li:last-of-type) {
    outline: 0.05em dashed canvasText;
  }
}

@layer scrollbar {
  @property --hue {
    initial-value: 0;
    syntax: '<number>';
    inherits: false;
  }
  @property --chroma {
    initial-value: 0;
    syntax: '<number>';
    inherits: true;
  }

  [data-sync-scrollbar='true'] {
    scrollbar-color: oklch(var(--lightness) var(--chroma) var(--hue)) #0000;
  }
  @supports (animation-timeline: scroll()) and (animation-range: 0% 100%) {
    [data-sync-scrollbar='true'][data-animate='true'] {
      timeline-scope: --list;
      scrollbar-color: oklch(var(--lightness) var(--chroma, 0) var(--hue)) #0000;
      animation-name: change, chroma-on, chroma-off;
      animation-fill-mode: both;
      animation-timing-function: linear;
      /* animation-timeline: scroll(root); */
      animation-range: entry 50% exit 50%, entry 40% entry 50%,
        exit 30% exit 40%;
      animation-timeline: --list;
      ul {
        view-timeline: --list;
      }
    }
  }

  @keyframes change {
    to {
      --hue: var(--end);
    }
  }
  @keyframes chroma-on {
    to {
      --chroma: 0.3;
    }
  }
  @keyframes chroma-off {
    to {
      --chroma: 0;
    }
  }
}

@layer effect {
  :root {
    --start: 0;
    --end: 360;
    --lightness: 65%;
    --base-chroma: 0.3;
  }
  [data-theme='dark'] {
    --lightness: 75%;
  }
  [data-theme='light'] {
    --lightness: 65%;
  }
  @media (prefers-color-scheme: dark) {
    --lightness: 75%;
  }
  ul {
    --step: calc((var(--end) - var(--start)) / (var(--count) - 1));
  }
  li:not(:last-of-type) {
    color: oklch(
      var(--lightness) var(--base-chroma)
        calc(var(--start) + (var(--step) * var(--i)))
    );
  }

  @supports (animation-timeline: scroll()) and (animation-range: 0% 100%) {
    [data-animate='true'] {
      li {
        opacity: 0.2;
        animation-name: brighten;

        &:first-of-type {
          --start-opacity: 1;
        }
        &:last-of-type {
          --brightness: 1;
          --end-opacity: 1;
        }
        animation-fill-mode: both;
        animation-timing-function: linear;
        animation-range: cover calc(50% - 1lh) calc(50% + 1lh);
        animation-timeline: view();
      }
    }

    @keyframes brighten {
      0% {
        opacity: var(--start-opacity, 0.2);
      }
      50% {
        opacity: 1;
        filter: brightness(var(--brightness, 1.2));
      }
      100% {
        opacity: var(--end-opacity, 0.2);
      }
    }
  }
}

@layer stick {
  section:first-of-type {
    --font-level: 6;
    display: flex;
    line-height: 1.25;
    width: 100%;
    padding-left: 5rem;
  }
  section:last-of-type {
    min-height: 100vh;
    display: flex;
    place-items: center;
    width: 100%;
    justify-content: center;

    h2 {
      --font-level: 6;
    }
  }
  main {
    width: 100%;
  }
  section:first-of-type h2 {
    position: sticky;
    top: calc(50% - 0.5lh);
    font-size: inherit;
    margin: 0;
    display: inline-block;
    height: fit-content;
    font-weight: 600;
  }
  ul {
    font-weight: 600;
    padding-inline: 0;
    margin: 0;
    list-style-type: none;
  }

  [data-snap='true'] {
    scroll-snap-type: y proximity;

    li {
      scroll-snap-align: center;
    }
  }

  h2,
  li:last-of-type {
    background: linear-gradient(
      canvasText 50%,
      color-mix(in oklch, canvas, canvasText 25%)
    );
    background-clip: text;
    color: #0000;
  }
}

@layer demo {
  header {
    min-height: 100vh;
    display: flex;
    place-items: center;
    width: 100%;
    padding-inline: 5rem;
  }

  footer {
    padding-block: 2rem;
    opacity: 0.5;
  }

  h1 {
    --font-size-min: 24;
    --font-level: 8;
    text-wrap: pretty;
    line-height: 0.8;
    margin: 0;
    background: linear-gradient(
      canvasText 60%,
      color-mix(in oklch, canvas, canvasText)
    );
    background-clip: text;
    color: #0000;
  }
}

@layer base {
  :root {
    --font-size-min: 14;
    --font-size-max: 20;
    --font-ratio-min: 1.1;
    --font-ratio-max: 1.33;
    --font-width-min: 375;
    --font-width-max: 1500;
  }

  html {
    color-scheme: light dark;
  }

  [data-theme='light'] {
    color-scheme: light only;
  }

  [data-theme='dark'] {
    color-scheme: dark only;
  }

  :where(.fluid) {
    --fluid-min: calc(
      var(--font-size-min) * pow(var(--font-ratio-min), var(--font-level, 0))
    );
    --fluid-max: calc(
      var(--font-size-max) * pow(var(--font-ratio-max), var(--font-level, 0))
    );
    --fluid-preferred: calc(
      (var(--fluid-max) - var(--fluid-min)) /
        (var(--font-width-max) - var(--font-width-min))
    );
    --fluid-type: clamp(
      (var(--fluid-min) / 16) * 1rem,
      ((var(--fluid-min) / 16) * 1rem) -
        (((var(--fluid-preferred) * var(--font-width-min)) / 16) * 1rem) +
        (var(--fluid-preferred) * var(--variable-unit, 100vi)),
      (var(--fluid-max) / 16) * 1rem
    );
    font-size: var(--fluid-type);
  }

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

  body {
    display: grid;
    place-items: center;
    background: light-dark(white, black);
    min-height: 100vh;
    font-family: 'Geist', 'SF Pro Text', 'SF Pro Icons', 'AOS Icons',
      'Helvetica Neue', Helvetica, Arial, sans-serif, system-ui;
  }

  body::before {
    --size: 45px;
    --line: color-mix(in hsl, canvasText, transparent 70%);
    content: '';
    height: 100vh;
    width: 100vw;
    position: fixed;
    background: linear-gradient(
          90deg,
          var(--line) 1px,
          transparent 1px var(--size)
        )
        50% 50% / var(--size) var(--size),
      linear-gradient(var(--line) 1px, transparent 1px var(--size)) 50% 50% /
        var(--size) var(--size);
    mask: linear-gradient(-20deg, transparent 50%, white);
    top: 0;
    transform-style: flat;
    pointer-events: none;
    z-index: -1;
  }

  .bear-link {
    color: canvasText;
    position: fixed;
    top: 1rem;
    left: 1rem;
    width: 48px;
    aspect-ratio: 1;
    display: grid;
    place-items: center;
    opacity: 0.8;
  }

  :where(.x-link, .bear-link):is(:hover, :focus-visible) {
    opacity: 1;
  }

  .bear-link svg {
    width: 75%;
  }

  /* Utilities */
  .sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
  }
}

div.tp-dfwv {
  position: fixed;
}

import { Pane } from 'https://cdn.skypack.dev/tweakpane@4.0.4'
import gsap from 'https://cdn.skypack.dev/gsap@3.12.0'
import ScrollTrigger from 'https://cdn.skypack.dev/gsap@3.12.0/ScrollTrigger'

const config = {
  theme: 'dark',
  animate: true,
  snap: true,
  start: gsap.utils.random(0, 100, 1),
  end: gsap.utils.random(900, 1000, 1),
  scroll: true,
  debug: false,
}

const ctrl = new Pane({
  title: 'Config',
  expanded: false,
})

let items
let scrollerScrub
let dimmerScrub
let chromaEntry
let chromaExit

const update = () => {
  document.documentElement.dataset.theme = config.theme
  document.documentElement.dataset.syncScrollbar = config.scroll
  document.documentElement.dataset.animate = config.animate
  document.documentElement.dataset.snap = config.snap
  document.documentElement.dataset.debug = config.debug
  document.documentElement.style.setProperty('--start', config.start)
  document.documentElement.style.setProperty('--hue', config.start)
  document.documentElement.style.setProperty('--end', config.end)

  if (!config.animate) {
    chromaEntry?.scrollTrigger.disable(true, false)
    chromaExit?.scrollTrigger.disable(true, false)
    dimmerScrub?.disable(true, false)
    scrollerScrub?.disable(true, false)
    gsap.set(items, { opacity: 1 })
    gsap.set(document.documentElement, { '--chroma': 0 })
  } else {
    gsap.set(items, { opacity: (i) => (i !== 0 ? 0.2 : 1) })
    dimmerScrub.enable(true, true)
    scrollerScrub.enable(true, true)
    chromaEntry.scrollTrigger.enable(true, true)
    chromaExit.scrollTrigger.enable(true, true)
  }
}

const sync = (event) => {
  if (
    !document.startViewTransition ||
    event.target.controller.view.labelElement.innerText !== 'Theme'
  )
    return update()
  document.startViewTransition(() => update())
}
ctrl.addBinding(config, 'animate', {
  label: 'Animate',
})
ctrl.addBinding(config, 'snap', {
  label: 'Snap',
})
ctrl.addBinding(config, 'start', {
  label: 'Hue Start',
  min: 0,
  max: 1000,
  step: 1,
})
ctrl.addBinding(config, 'end', {
  label: 'Hue End',
  min: 0,
  max: 1000,
  step: 1,
})
ctrl.addBinding(config, 'scroll', {
  label: 'Scrollbar',
})
ctrl.addBinding(config, 'debug', {
  label: 'Debug',
})

ctrl.addBinding(config, 'theme', {
  label: 'Theme',
  options: {
    System: 'system',
    Light: 'light',
    Dark: 'dark',
  },
})

ctrl.on('change', sync)

// backfill the scroll functionality with GSAP
if (
  !CSS.supports('(animation-timeline: scroll()) and (animation-range: 0% 100%)')
) {
  gsap.registerPlugin(ScrollTrigger)

  // animate the items with GSAP if there's no CSS support
  items = gsap.utils.toArray('ul li')

  gsap.set(items, { opacity: (i) => (i !== 0 ? 0.2 : 1) })

  const dimmer = gsap
    .timeline()
    .to(items.slice(1), {
      opacity: 1,
      stagger: 0.5,
    })
    .to(
      items.slice(0, items.length - 1),
      {
        opacity: 0.2,
        stagger: 0.5,
      },
      0
    )

  dimmerScrub = ScrollTrigger.create({
    trigger: items[0],
    endTrigger: items[items.length - 1],
    start: 'center center',
    end: 'center center',
    animation: dimmer,
    scrub: 0.2,
  })

  // register scrollbar changer
  const scroller = gsap.timeline().fromTo(
    document.documentElement,
    {
      '--hue': config.start,
    },
    {
      '--hue': config.end,
      ease: 'none',
    }
  )

  scrollerScrub = ScrollTrigger.create({
    trigger: items[0],
    endTrigger: items[items.length - 1],
    start: 'center center',
    end: 'center center',
    animation: scroller,
    scrub: 0.2,
  })

  chromaEntry = gsap.fromTo(
    document.documentElement,
    {
      '--chroma': 0,
    },
    {
      '--chroma': 0.3,
      ease: 'none',
      scrollTrigger: {
        scrub: 0.2,
        trigger: items[0],
        start: 'center center+=40',
        end: 'center center',
      },
    }
  )
  chromaExit = gsap.fromTo(
    document.documentElement,
    {
      '--chroma': 0.3,
    },
    {
      '--chroma': 0,
      ease: 'none',
      scrollTrigger: {
        scrub: 0.2,
        trigger: items[items.length - 2],
        start: 'center center',
        end: 'center center-=40',
      },
    }
  )
}
// run it
update()

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