app/src/components/Accordion.astro

---
const { title, open = false, class: className, ...props } = Astro.props;
const wrapperClass = ["accordion", className].filter(Boolean).join(" ");
---
<details class={wrapperClass} open={open} {...props}>
  <summary class="accordion__summary">
    <span class="accordion__title">{title}</span>
    <svg class="accordion__chevron" viewBox="0 0 24 24" width="18" height="18" aria-hidden="true">
      <path d="M6 9l6 6 6-6" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" />
    </svg>
  </summary>
  <div class="accordion__content-wrapper">
    <div class="accordion__content">
      <slot />
    </div>
  </div>
</details>

<script>
  // Animate open/close by transitioning explicit height
  document.addEventListener('DOMContentLoaded', () => {
    const accordions = document.querySelectorAll('.accordion') as NodeListOf<HTMLDetailsElement>;
    accordions.forEach((acc) => {
      const summary = acc.querySelector('summary.accordion__summary') as HTMLElement | null;
      const wrapper = acc.querySelector('.accordion__content-wrapper') as HTMLElement | null;
      const content = acc.querySelector('.accordion__content') as HTMLElement | null;
      if (!summary || !wrapper || !content) return;

      const reduceMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
      const duration = reduceMotion ? 0 : 240;

      // Initial state
      wrapper.style.overflow = 'hidden';
      wrapper.style.height = acc.open ? 'auto' : '0px';

      const open = () => {
        wrapper.style.height = '0px';
        void wrapper.offsetHeight; // reflow
        const target = content.scrollHeight;
        wrapper.style.transition = `height ${duration}ms ease`;
        wrapper.style.height = `${target}px`;
        const onEnd = () => {
          wrapper.style.transition = '';
          wrapper.style.height = 'auto';
          wrapper.removeEventListener('transitionend', onEnd);
        };
        wrapper.addEventListener('transitionend', onEnd);
      };

      const close = () => {
        const start = wrapper.offsetHeight || content.scrollHeight;
        wrapper.style.height = `${start}px`;
        void wrapper.offsetHeight; // reflow
        wrapper.style.transition = `height ${duration}ms ease`;
        wrapper.style.height = '0px';
        const onEnd = () => {
          wrapper.style.transition = '';
          wrapper.removeEventListener('transitionend', onEnd);
          acc.removeAttribute('open');
        };
        wrapper.addEventListener('transitionend', onEnd);
      };

      summary.addEventListener('click', (e) => {
        e.preventDefault();
        if (acc.open) {
          close();
        } else {
          acc.setAttribute('open', '');
          open();
        }
      });
    });
  });
  </script>

<style>
  .accordion {
    margin: 0 0 var(--spacing-4);
    padding: 0;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    background: var(--surface-bg);
    transition: box-shadow 180ms ease, border-color 180ms ease;
  }

  .accordion[open] {
    border-color: color-mix(in oklab, var(--border-color), var(--primary-color) 20%);
  }

  .accordion__summary {
    margin: 0;
    list-style: none;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 4px;
    padding: 10px 8px;
    cursor: pointer;
    color: var(--text-color);
    user-select: none;
  }

  /* Remove conditional padding to avoid jump on close */

  /* Remove native marker */
  .accordion__summary::-webkit-details-marker {
    display: none;
  }
  .accordion__summary::marker {
    content: "";
  }

  .accordion__title {
    font-weight: 600;
  }

  .accordion__chevron {
    flex: 0 0 auto;
    transition: transform 220ms ease;
    opacity: .85;
  }

  .accordion[open] .accordion__chevron {
    transform: rotate(180deg);
  }

  /* Animated expand/collapse using height (controlled in JS) */
  .accordion__content-wrapper {
    overflow: hidden;
    height: 0px;
    will-change: height;
    position: relative;
  }

  .accordion__content {
    margin: 0;
    padding: 0;
  }

  /* Ensure the very last slotted element has no bottom spacing */
  .accordion .accordion__content > :global(*:last-child) {
    padding-bottom: 0 !important;
    margin-bottom: 0 !important;
  }

  /* Ensure the very first slotted element has no top spacing */
  .accordion .accordion__content > :global(*:first-child) {
    margin-top: 0 !important;
  }

  /* Content padding: default for direct children, opt-out for code/tables */
  .accordion .accordion__content > :global(*) {
    padding: 8px;
  }
  .accordion .accordion__content > :global(.table-scroll),
  .accordion .accordion__content > :global(pre),
  .accordion .accordion__content > :global(.code-card) {
    padding: 0;
  }

  /* Separator between header and content when open (edge-to-edge) */
  .accordion[open] .accordion__content-wrapper::before {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    top: 0px; /* space below header */
    height: 1px;
    background: var(--border-color);
    pointer-events: none;
  }

  /* Focus styles for accessibility */
  .accordion__summary:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 3px;
    border-radius: 8px;
  }


</style>