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CSS

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HTML 

              
                <main class="layout-stack">
  <div id="collection-1" class="collection layout-layer">
    <scrolly-rail data-control-previous="collection-1-btn-previous" data-control-next="collection-1-btn-next">
      <ul class="collection-list" role="list">
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Herbie Carpenter</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Stunt Coordinator</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Stunts</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Los Angeles, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Felicity Guest</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Production Designer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Burbank, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Doug Hammond</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Assistant Director</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Los Angeles, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Deb Blanchard</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Director</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>New York, NY</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Patty Verona</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Composer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Music</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Portland, ME</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Gregory Brown</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Executive Producer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Burbank, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Beverly Mirren-Henderson</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Accounting</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Finance</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Seattle, WA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Adam East</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Costume Designer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Design</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Burbank, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Ellie Morelli</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Animator</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Design</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Burbank, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Devon Williams</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Lightning Technician</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>New York, NY</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Patty Verona</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Composer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Music</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Portland, ME</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
        <li>
          <x-card>
            <figure></figure>
            <div class="content">
              <h2><a href="#">Gregory Brown</a></h2>
              <dl class="meta">
                <div class="role">
                  <dt>Role</dt>
                  <dd>Executive Producer</dd>
                </div>
                <div>
                  <dt>Team</dt>
                  <dd>Production</dd>
                </div>
                <div>
                  <dt>Location</dt>
                  <dd>Burbank, CA</dd>
                </div>
              </dl>
            </div>
          </x-card>
        </li>
      </ul>
    </scrolly-rail>

    <button data-bound class="btn-scrolly-rail btn-scrolly-rail--previous animate-appearance" id="collection-1-btn-previous">
      <span class="visually-hidden">Scroll previous items into view</span>
      <svg class="icon" aria-hidden="true" width="15" height="15" viewBox="0 0 15 15" fill="none" xmlns="http://www.w3.org/2000/svg">
        <path d="M6.85355 3.14645C7.04882 3.34171 7.04882 3.65829 6.85355 3.85355L3.70711 7H12.5C12.7761 7 13 7.22386 13 7.5C13 7.77614 12.7761 8 12.5 8H3.70711L6.85355 11.1464C7.04882 11.3417 7.04882 11.6583 6.85355 11.8536C6.65829 12.0488 6.34171 12.0488 6.14645 11.8536L2.14645 7.85355C1.95118 7.65829 1.95118 7.34171 2.14645 7.14645L6.14645 3.14645C6.34171 2.95118 6.65829 2.95118 6.85355 3.14645Z" fill="currentColor" fill-rule="evenodd" clip-rule="evenodd"></path>
      </svg>
      </svg>
    </button>
    <button class="btn-scrolly-rail btn-scrolly-rail--next animate-appearance" id="collection-1-btn-next">
      <span class="visually-hidden">Scroll next items into view</span>
      <svg class="icon" aria-hidden="true" width="15" height="15" viewBox="0 0 15 15" fill="none" xmlns="http://www.w3.org/2000/svg">
        <path d="M8.14645 3.14645C8.34171 2.95118 8.65829 2.95118 8.85355 3.14645L12.8536 7.14645C13.0488 7.34171 13.0488 7.65829 12.8536 7.85355L8.85355 11.8536C8.65829 12.0488 8.34171 12.0488 8.14645 11.8536C7.95118 11.6583 7.95118 11.3417 8.14645 11.1464L11.2929 8H2.5C2.22386 8 2 7.77614 2 7.5C2 7.22386 2.22386 7 2.5 7H11.2929L8.14645 3.85355C7.95118 3.65829 7.95118 3.34171 8.14645 3.14645Z" fill="currentColor" fill-rule="evenodd" clip-rule="evenodd"></path>
      </svg>
    </button>
  </div>

  <div id="collection-2" class="collection layout-stack">
    <div class="scrolly-rail-wrapper">
      <scrolly-rail data-control-previous="collection-2-btn-previous" data-control-next="collection-2-btn-next">
        <ol class="collection-list" role="list">
          <li class="placeholder-item">1</li>
          <li class="placeholder-item">2</li>
          <li class="placeholder-item">3</li>
          <li class="placeholder-item">4</li>
          <li class="placeholder-item">5</li>
          <li class="placeholder-item">6</li>
          <li class="placeholder-item">7</li>
          <li class="placeholder-item">8</li>
          <li class="placeholder-item">9</li>
          <li class="placeholder-item">10</li>
          <li class="placeholder-item">11</li>
          <li class="placeholder-item">12</li>
          <li class="placeholder-item">13</li>
          <li class="placeholder-item">14</li>
          <li class="placeholder-item">15</li>
          <li class="placeholder-item">16</li>
          <li class="placeholder-item">17</li>
          <li class="placeholder-item">18</li>
          <li class="placeholder-item">19</li>
          <li class="placeholder-item">20</li>
          <li class="placeholder-item">21</li>
          <li class="placeholder-item">22</li>
          <li class="placeholder-item">23</li>
          <li class="placeholder-item">24</li>
        </ol>
      </scrolly-rail>
    </div>

    <div class="scrolly-rail-controls">
      <button data-bound class="btn-scrolly-rail btn-scrolly-rail--previous animate-fade" id="collection-2-btn-previous">
        <span class="visually-hidden">Scroll previous items into view</span>
        <svg class="icon" aria-hidden="true" width="15" height="15" viewBox="0 0 15 15" fill="none" xmlns="http://www.w3.org/2000/svg">
          <path d="M6.85355 3.14645C7.04882 3.34171 7.04882 3.65829 6.85355 3.85355L3.70711 7H12.5C12.7761 7 13 7.22386 13 7.5C13 7.77614 12.7761 8 12.5 8H3.70711L6.85355 11.1464C7.04882 11.3417 7.04882 11.6583 6.85355 11.8536C6.65829 12.0488 6.34171 12.0488 6.14645 11.8536L2.14645 7.85355C1.95118 7.65829 1.95118 7.34171 2.14645 7.14645L6.14645 3.14645C6.34171 2.95118 6.65829 2.95118 6.85355 3.14645Z" fill="currentColor" fill-rule="evenodd" clip-rule="evenodd"></path>
        </svg>
        </svg>
      </button>
      <button class="btn-scrolly-rail btn-scrolly-rail--next animate-fade" id="collection-2-btn-next">
        <span class="visually-hidden">Scroll next items into view</span>
        <svg class="icon" aria-hidden="true" width="15" height="15" viewBox="0 0 15 15" fill="none" xmlns="http://www.w3.org/2000/svg">
          <path d="M8.14645 3.14645C8.34171 2.95118 8.65829 2.95118 8.85355 3.14645L12.8536 7.14645C13.0488 7.34171 13.0488 7.65829 12.8536 7.85355L8.85355 11.8536C8.65829 12.0488 8.34171 12.0488 8.14645 11.8536C7.95118 11.6583 7.95118 11.3417 8.14645 11.1464L11.2929 8H2.5C2.22386 8 2 7.77614 2 7.5C2 7.22386 2.22386 7 2.5 7H11.2929L8.14645 3.85355C7.95118 3.65829 7.95118 3.34171 8.14645 3.14645Z" fill="currentColor" fill-rule="evenodd" clip-rule="evenodd"></path>
        </svg>
      </button>
    </div>
  </div>
</main>
!

CSS 

              
                @layer base, patterns, components, utils;

@layer components {
  /* Base scrolly-rail component styles */
  scrolly-rail {
    display: flex;
    overflow-x: auto;
    overscroll-behavior-x: contain;
    scroll-snap-type: x mandatory;

    @media (prefers-reduced-motion: no-preference) {
      scroll-behavior: smooth;
    }
  }
}

@layer base {
  :root {
    --text-1: #0f172a;
    --text-2: #64748b;
    --surface-1: #ffffff;
    --surface-2: #f8fafc;
    --surface-3: #f1f5f9;
    --surface-4: #cbd5e1;
    --surface-5: #64748b;
    --surface-translucent: hsla(210 40% 98% / 0.8);

    --border-color: var(--surface-5);
    --border-color-subtle: var(--surface-4);
    --border-color-highlight: var(--surface-3);
    --scrollbar-color: var(--text-2) var(--surface-3);

    --space-xs: 0.25rem;
    --space-s: 0.5rem;
    --space-m: 1rem;
    --space-l: 2rem;
    --space-xl: 3rem;

    --ease-out-quart: cubic-bezier(0.25, 1, 0.5, 1);
    --ease-out-back: cubic-bezier(0.34, 1.56, 0.64, 1);
  }

  * {
    box-sizing: border-box;
    margin: 0;
  }

  html,
  body {
    height: 100%;
  }

  body {
    display: grid;
    margin: 0;
    font-family: system-ui, sans-serif;
    color: var(--text-1);
    background-color: var(--surface-2);
  }

  :where(ul, ol)[role="list"] {
    list-style: none;
    padding-inline-start: unset;
  }
}

@layer utils {
  .visually-hidden {
    clip: rect(0 0 0 0);
    clip-path: inset(50%);
    height: 1px;
    overflow: hidden;
    position: absolute;
    white-space: nowrap;
    width: 1px;
  }
}

@layer patterns {
  .layout-stack > * + * {
    margin-block-start: var(--stack-space, 1rem);
  }

  .layout-layer {
    display: grid;
    grid-template-areas: "box";

    > * {
      grid-area: box;
    }
  }
}

@layer components {
  .icon {
    --_size: var(--icon-size, 1em);
    width: var(--_size);
    height: var(--_size);
  }

  /* Custom component styles */
  scrolly-rail {
    --_block-gutter: var(--space-m);
    --_inline-gutter: var(--space-l);

    scroll-padding-inline-start: var(--_inline-gutter);
    scrollbar-color: var(--scrollbar-color);
    padding-inline: var(--_inline-gutter);
    padding-block: var(--_block-gutter);
    margin-block: calc(var(--_block-gutter) * -1);
  }

  .btn-scrolly-rail {
    --icon-size: 1.25rem;
    --x-offset-direction: 1;
    --_size: calc(var(--icon-size, 1rem) * 2);
    --_x-offset: calc(6px * var(--x-offset-direction));
    position: relative;
    overflow: hidden;
    display: grid;
    place-items: center;
    place-content: center;
    inline-size: var(--_size);
    block-size: var(--_size);
    border-radius: 50%;
    color: var(--border-color);
    border: 1px solid currentcolor;
    background: var(--surface-translucent);
    backdrop-filter: blur(2px);
    box-shadow: hsla(0 0% 0% / 0.1) 0 4px 8px -3px;
    cursor: pointer;
    touch-action: manipulation;

    .icon {
      transition: translate 300ms var(--ease-out-back);
    }

    &:not([data-bound]):active .icon {
      translate: calc(-10% * var(--x-offset-direction)) 0;
    }
  }

  .btn-scrolly-rail[class*="animate"] {
    transition: 225ms var(--ease-out-quart);
  }

  .btn-scrolly-rail.animate-fade {
    transition-property: border-color, color, box-shadow;

    &[data-bound] {
      color: var(--surface-4);
      box-shadow: none;
    }
  }

  .btn-scrolly-rail.animate-appearance {
    transition-property: display, opacity, translate, scale;
    transition-behavior: allow-discrete;

    &[data-bound] {
      display: none;
      opacity: 0;
      scale: 0.5;
    }

    @starting-style {
      opacity: 0;
      translate: var(--_x-offset) 0;

      .icon {
        translate: calc(100% * var(--x-offset-direction)) 0;
      }
    }
  }

  x-card {
    position: relative;
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 1rem;
    padding: 1rem;
    background: linear-gradient(var(--surface-1), var(--surface-1)) padding-box,
      linear-gradient(
          135deg,
          var(--border-color-subtle),
          var(--border-color-highlight) 40% 60%,
          var(--border-color-subtle)
        )
        border-box;
    border: 1px solid transparent;
    box-shadow: hsla(0 0% 0% / 0.06) 0 4px 6px -3px;
    border-radius: 0.65rem;

    &:focus-within {
      outline: 5px auto Highlight;
      outline: 5px auto -webkit-focus-ring-color;
    }

    .content {
      display: grid;
      gap: 0.4rem;
    }

    h2 {
      grid-row: 1;
      margin: 0;
      font-size: 1.2em;
      font-weight: 500;
      letter-spacing: -0.01em;

      a {
        color: currentcolor;
        text-decoration: none;
        outline: none;
      }
    }

    figure {
      overflow: hidden;
      aspect-ratio: 1;
      border-radius: 50%;
      inline-size: 4rem;
      margin: 0;
      background: var(--border-color-highlight);
      border: 1px solid var(--border-color-subtle);
    }

    .meta {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(min(8rem, 100%), 1fr));
      justify-items: start;
      gap: 0.4rem;
      line-height: 1.2;

      .role {
        grid-column: 1 / -1;
      }

      dt {
        font-size: 0.8em;
        margin-block-end: 0.125em;
        color: var(--text-2);
      }
    }
  }
}

main {
  --stack-space: var(--space-xl);
  margin-block: auto;
  padding-block: var(--space-xl) var(--space-m);
}

.collection-list {
  display: flex;
}

.collection-list > li {
  display: grid;
  scroll-snap-align: start;
}

#collection-1 {
  --control-margin-offset: var(--space-s);

  x-card {
    inline-size: clamp(20rem, 1rem + 50vw, 25rem);
  }

  .collection-list {
    gap: var(--space-s);
  }

  .btn-scrolly-rail--previous {
    place-self: center start;
    margin-inline-start: var(--control-margin-offset);
  }

  .btn-scrolly-rail--next {
    --x-offset-direction: -1;
    place-self: center end;
    margin-inline-end: var(--control-margin-offset);
  }
}

#collection-2 {
  position: relative;
  inline-size: min(50rem, 100% - var(--space-l) * 2);
  margin-inline: auto;

  .scrolly-rail-wrapper {
    display: grid;
    padding-block: var(--space-m);
    border-inline: 1px dashed var(--border-color);
  }

  .collection-list {
    gap: var(--space-m);
  }

  .placeholder-item {
    display: grid;
    place-items: center;
    padding: 1rem;
    inline-size: 8rem;
    aspect-ratio: 4 / 5;
    border: 1px solid var(--border-color);
    border-radius: 0.4rem;
  }

  .scrolly-rail-controls {
    --stack-space: var(--space-s);
    display: flex;
    gap: var(--space-s);
    inline-size: fit-content;
    margin-inline: auto;
  }

  .btn-scrolly-rail--previous {
    margin-inline-start: var(--control-margin-offset);
  }

  .btn-scrolly-rail--next {
    --x-offset-direction: -1;
    margin-inline-end: var(--control-margin-offset);
  }
}
!

JS 

              
                class ScrollyRail extends HTMLElement {
  static register(tag = "scrolly-rail") {
    if ("customElements" in window) {
      customElements.define(tag, this);
    }
  }

  get items() {
    const els = [...this.children];
    let arr;

    /**
     * Check if direct child is a wrapper element that contains children.
     * Otherwise, return direct children.
     */
    if (els.length === 1 && els[0].children.length > 0) {
      arr = [...els[0].children];
    } else {
      arr = [...els];
    }

    return arr;
  }

  connectedCallback() {
    if (!this.items) return;

    this.prevBtn = document.getElementById(this.dataset.controlPrevious);
    this.nextBtn = document.getElementById(this.dataset.controlNext);

    if (this.prevBtn) {
      this.observeScrollStart();
      this.handleClickPrevious = () => this.goToPrevious();
      this.prevBtn.addEventListener("click", this.handleClickPrevious);
    }

    if (this.nextBtn) {
      this.observeScrollEnd();
      this.handleClickNext = () => this.goToNext();
      this.nextBtn.addEventListener("click", this.handleClickNext);
    }

    this.resizeObserver = new ResizeObserver(() => this.init());
    this.resizeObserver.observe(this);
  }

  disconnectedCallback() {
    this.resizeObserver.disconnect();

    if (this.prevBtn) {
      this.scrollStartObserver.disconnect();
      this.prevBtn.removeEventListener("click", this.handleClickPrevious);
    }

    if (this.nextBtn) {
      this.scrollEndObserver.disconnect();
      this.nextBtn.removeEventListener("click", this.handleClickNext);
    }
  }

  init() {
    this.bounds = this.getBounds();
    this.step = this.getVisibleItemCount();
  }

  getBounds() {
    const { left, right } = this.getBoundingClientRect();
    return {
      left: Math.round(left),
      right: Math.round(right)
    };
  }

  getVisibleItemCount() {
    let count = 0;

    for (let i = 0; i < this.items.length; i++) {
      const { left, right } = this.items[i].getBoundingClientRect();

      if (Math.round(right) > this.bounds.right) break;
      if (Math.round(left) >= this.bounds.left) count++;
    }

    return count;
  }

  handleScrollIntoView(item, sibling) {
    /*
     * If singular visible item is selected and overflows, navigate to a sibling item.
     */
    const target = this.step > 0 ? item : sibling;

    target?.scrollIntoView({
      block: "nearest",
      inline: "start"
    });
  }

  goToPrevious() {
    for (let i = this.items.length - 1; i >= 0; i--) {
      const { left } = this.items[i].getBoundingClientRect();

      if (Math.round(left) < this.bounds.left) {
        /*
         * Find the target item to align at start position.
         * Prevent the item at current index from overflowing.
         * Ensure target item index is always 0 or greater.
         */
        const target = this.items[Math.max(i - this.step + 1, 0)];

        this.handleScrollIntoView(target, target.previousElementSibling);
        break;
      }
    }
  }

  goToNext() {
    for (let i = 0; i < this.items.length; i++) {
      const item = this.items[i];
      const { right } = item.getBoundingClientRect();

      if (Math.round(right) > this.bounds.right) {
        this.handleScrollIntoView(item, item.nextElementSibling);
        break;
      }
    }
  }

  observeScrollStart() {
    const firstItem = this.items[0];
    this.scrollStartObserver = this.setupObserver(this.prevBtn, firstItem);
    this.scrollStartObserver.observe(firstItem);
  }

  observeScrollEnd() {
    const lastItem = this.items[this.items.length - 1];
    this.scrollEndObserver = this.setupObserver(this.nextBtn, lastItem);
    this.scrollEndObserver.observe(lastItem);
  }

  /*
   * Observe scroll bounds of first and/or last element.
   * Toggle attribute on a button control when its respective scroll bound is reached.
   */
  setupObserver(btn, item) {
    const callback = ([entry]) => {
      btn.toggleAttribute(
        "data-bound",
        entry.target === item && entry.isIntersecting
      );
    };

    const options = {
      root: this,
      threshold: 1
    };

    return new IntersectionObserver(callback, options);
  }
}

ScrollyRail.register();
!
999px

Console