Bootstrap 5 Accordion Image Gallery

<section class="wdw-stage">
  <div class="container w-100" style="max-width:1100px">
    <div class="d-flex flex-wrap align-items-end justify-content-between gap-2 mb-4">
      <div><span class="wdw-eyebrow">Gallery</span><h1 class="wdw-heading h2 mt-1 mb-0">Colour studies</h1></div>
      <p class="wdw-muted mb-0 small">Hover, tap or focus a panel to expand it.</p>
    </div>
    <div class="ag-gallery" id="agGallery" role="group" aria-label="Image gallery">
        <button type="button" class="ag-item is-open" aria-expanded="true" style="--img:url('https://images.unsplash.com/photo-1499198116522-4a6235013d63?auto=format&fit=crop&w=900&q=75')">
          <span class="ag-caption"><span class="ag-num">01</span><strong class="d-block">Studio stool</strong><span class="small">Oak and rattan, hand finished</span></span>
        </button>
        <button type="button" class="ag-item" aria-expanded="false" style="--img:url('https://images.unsplash.com/photo-1492760864391-753aaae87234?auto=format&fit=crop&w=900&q=75')">
          <span class="ag-caption"><span class="ag-num">02</span><strong class="d-block">Spiral stair</strong><span class="small">Warm curves, bold colour</span></span>
        </button>
        <button type="button" class="ag-item" aria-expanded="false" style="--img:url('https://images.unsplash.com/photo-1503631285924-e1544dce8b28?auto=format&fit=crop&w=900&q=75')">
          <span class="ag-caption"><span class="ag-num">03</span><strong class="d-block">Berry smoothie</strong><span class="small">Still life in red</span></span>
        </button>
        <button type="button" class="ag-item" aria-expanded="false" style="--img:url('https://images.unsplash.com/photo-1510425463958-dcced28da480?auto=format&fit=crop&w=900&q=75')">
          <span class="ag-caption"><span class="ag-num">04</span><strong class="d-block">Floating banana</strong><span class="small">Playful product shot</span></span>
        </button>
        <button type="button" class="ag-item" aria-expanded="false" style="--img:url('https://images.unsplash.com/photo-1503602642458-232111445657?auto=format&fit=crop&w=900&q=75')">
          <span class="ag-caption"><span class="ag-num">05</span><strong class="d-block">Bar stool</strong><span class="small">Pale ash on soft blue</span></span>
        </button>
        </div>
  </div>
</section>

/* Web Designer Wall library style — shared base for every Bootstrap 5 snippet.
   Indigo accent, Plus Jakarta Sans, soft cards, pill buttons. Works in light and dark. */
@import url("https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap");

:root,
[data-bs-theme="light"] {
  --wdw-font: "Plus Jakarta Sans", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --bs-body-font-family: var(--wdw-font);
  --bs-primary: #4f46e5;
  --bs-primary-rgb: 79, 70, 229;
  --bs-primary-text-emphasis: #3730a3;
  --bs-primary-bg-subtle: #eef2ff;
  --bs-primary-border-subtle: #c7d2fe;
  --bs-link-color: #4f46e5;
  --bs-link-color-rgb: 79, 70, 229;
  --bs-link-hover-color: #4338ca;
  --bs-link-hover-color-rgb: 67, 56, 202;
  --bs-focus-ring-color: rgba(79, 70, 229, 0.25);
  --bs-border-radius: 0.75rem;
  --bs-border-radius-lg: 1rem;
  --bs-border-radius-xl: 1.25rem;
  --wdw-radius-card: 1.25rem;
  --wdw-shadow: 0 1px 2px rgba(16, 24, 40, 0.05), 0 16px 40px -16px rgba(16, 24, 40, 0.22);
  --wdw-shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06), 0 4px 12px -4px rgba(16, 24, 40, 0.12);
  --wdw-stage: #f5f6fb;
}

[data-bs-theme="dark"] {
  --bs-primary: #818cf8;
  --bs-primary-rgb: 129, 140, 248;
  --bs-primary-text-emphasis: #c7d2fe;
  --bs-primary-bg-subtle: rgba(129, 140, 248, 0.14);
  --bs-primary-border-subtle: rgba(129, 140, 248, 0.35);
  --bs-link-color: #a5b4fc;
  --bs-link-color-rgb: 165, 180, 252;
  --bs-link-hover-color: #c7d2fe;
  --bs-link-hover-color-rgb: 199, 210, 254;
  --bs-focus-ring-color: rgba(129, 140, 248, 0.35);
  --wdw-shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 16px 40px -16px rgba(0, 0, 0, 0.7);
  --wdw-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 12px -4px rgba(0, 0, 0, 0.5);
  --wdw-stage: #0f1117;
}

body { font-family: var(--wdw-font); -webkit-font-smoothing: antialiased; }

/* Bootstrap compiles its blue into these components; point them at the accent. */
.btn-primary {
  --bs-btn-bg: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: #4338ca; --bs-btn-hover-border-color: #4338ca;
  --bs-btn-active-bg: #3730a3; --bs-btn-active-border-color: #3730a3;
  --bs-btn-disabled-bg: var(--bs-primary); --bs-btn-disabled-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
[data-bs-theme="dark"] .btn-primary { --bs-btn-color: #0f1117; --bs-btn-hover-bg: #a5b4fc; --bs-btn-hover-border-color: #a5b4fc; --bs-btn-hover-color: #0f1117; --bs-btn-active-color: #0f1117; }
.btn-outline-primary {
  --bs-btn-color: var(--bs-primary); --bs-btn-border-color: var(--bs-primary);
  --bs-btn-hover-bg: var(--bs-primary); --bs-btn-hover-border-color: var(--bs-primary);
  --bs-btn-active-bg: var(--bs-primary); --bs-btn-active-border-color: var(--bs-primary);
  --bs-btn-focus-shadow-rgb: var(--bs-primary-rgb);
}
.btn { --bs-btn-font-weight: 600; min-height: 44px; display: inline-flex; align-items: center; justify-content: center; gap: .5rem; }
.btn-sm { min-height: 36px; }
.form-control, .form-select { min-height: 44px; border-radius: .75rem; }
.form-control:focus, .form-select:focus, .form-check-input:focus { border-color: rgba(var(--bs-primary-rgb), .6); box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.form-check-input:checked { background-color: var(--bs-primary); border-color: var(--bs-primary); }
.nav-pills { --bs-nav-pills-link-active-bg: var(--bs-primary); }
.nav { --bs-nav-link-color: var(--bs-secondary-color); --bs-nav-link-hover-color: var(--bs-emphasis-color); }
.pagination { --bs-pagination-active-bg: var(--bs-primary); --bs-pagination-active-border-color: var(--bs-primary); --bs-pagination-color: var(--bs-body-color); --bs-pagination-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.progress, .progress-stacked { --bs-progress-bar-bg: var(--bs-primary); }
.list-group { --bs-list-group-active-bg: var(--bs-primary); --bs-list-group-active-border-color: var(--bs-primary); }
.dropdown-menu { --bs-dropdown-link-active-bg: var(--bs-primary); border-radius: .875rem; box-shadow: var(--wdw-shadow-sm); }
.accordion { --bs-accordion-active-bg: var(--bs-primary-bg-subtle); --bs-accordion-active-color: var(--bs-primary-text-emphasis); --bs-accordion-btn-focus-box-shadow: 0 0 0 .25rem var(--bs-focus-ring-color); }
.badge { font-weight: 600; }

/* Library building blocks — use these instead of re-inventing them per snippet. */
.wdw-stage { min-height: 100vh; display: flex; align-items: center; background: var(--wdw-stage); padding-block: 3rem; }
.wdw-card { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: var(--wdw-radius-card); box-shadow: var(--wdw-shadow); }
.wdw-card-sm { background: var(--bs-body-bg); border: 1px solid var(--bs-border-color-translucent); border-radius: 1rem; box-shadow: var(--wdw-shadow-sm); }
.wdw-aurora { position: relative; color: #fff; background: radial-gradient(60% 55% at 100% 0, #818cf8 0, transparent 70%), radial-gradient(65% 60% at 0 100%, #ec4899 0, transparent 65%), #1e1b4b; }
.wdw-eyebrow { display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--bs-primary); }
.wdw-heading { font-weight: 800; letter-spacing: -.02em; color: var(--bs-emphasis-color); }
.wdw-muted { color: var(--bs-secondary-color); }
.wdw-icon { width: 2.75rem; height: 2.75rem; flex: none; display: inline-flex; align-items: center; justify-content: center; border-radius: .875rem; background: var(--bs-primary-bg-subtle); color: var(--bs-primary); }

/* Component */
.ag-gallery { display: flex; gap: .75rem; height: 460px; }
.ag-item { position: relative; flex: 1 1 0; min-width: 0; border: 0; padding: 0; border-radius: 1.25rem; overflow: hidden; background: var(--img) center/cover no-repeat #cbd5e1; cursor: pointer; text-align: left; color: #fff; transition: flex-grow .55s cubic-bezier(.4,0,.2,1), box-shadow .3s; box-shadow: var(--wdw-shadow-sm); }
.ag-item.is-open { flex-grow: 5; box-shadow: var(--wdw-shadow); }
.ag-item::after { content: ""; position: absolute; inset: 0; background: linear-gradient(180deg, transparent 45%, rgba(10,12,30,.75)); opacity: .55; transition: opacity .4s; }
.ag-item.is-open::after { opacity: 1; }
.ag-item:focus-visible { outline: 3px solid var(--bs-primary); outline-offset: 3px; }
.ag-caption { position: absolute; left: 1.25rem; right: 1.25rem; bottom: 1.1rem; z-index: 1; opacity: 0; transform: translateY(8px); transition: opacity .35s .15s, transform .35s .15s; }
.ag-item.is-open .ag-caption { opacity: 1; transform: none; }
.ag-num { display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .1em; opacity: .8; margin-bottom: .25rem; }
.ag-caption strong { font-size: 1.25rem; white-space: nowrap; }
.ag-caption .small { opacity: .85; white-space: nowrap; }
@media (max-width: 767.98px) {
  .ag-gallery { flex-direction: column; height: 520px; }
  .ag-item { border-radius: 1rem; }
  .ag-item.is-open { flex-grow: 4; }
}
@media (prefers-reduced-motion: reduce) { .ag-item, .ag-caption { transition: none; } }

(function () {
  function initAccordionGallery() {
    var g = document.getElementById('agGallery');
    if (!g) return;
    var items = g.querySelectorAll('.ag-item');
    function open(it) {
      items.forEach(function (x) { var on = x === it; x.classList.toggle('is-open', on); x.setAttribute('aria-expanded', on); });
    }
    items.forEach(function (it) {
      it.addEventListener('mouseenter', function () { open(it); });
      it.addEventListener('focus', function () { open(it); });
      it.addEventListener('click', function () { open(it); });
    });
  }
  initAccordionGallery();
})();