<form class="csb-sug" role="search" autocomplete="off">
  <label class="csb-sr" for="csb-sug-i">Search</label>
  <input
    id="csb-sug-i"
    type="search"
    name="q"
    placeholder="Try 'flex' or 'grid'"
    aria-controls="csb-sug-list"
    aria-expanded="false"
    aria-autocomplete="list"
  />
  <ul id="csb-sug-list" class="csb-sug-list" role="listbox" hidden>
    <li role="option">Flex container</li>
    <li role="option">Flex item</li>
    <li role="option">Grid container</li>
    <li role="option">Grid template</li>
    <li role="option">Grid auto-flow</li>
  </ul>
</form>

.csb-sug { position: relative; display: inline-block; }
.csb-sug input {
  width: 240px; padding: 10px 14px;
  background: #1a1a28;
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 10px;
  color: #f0eeff; font: 500 14px/1 system-ui, sans-serif;
  outline: none;
  transition: border-color 0.2s, border-radius 0.15s;
}
.csb-sug input::placeholder { color: #b8b6d4; }
.csb-sug input:focus { border-color: #7c6cff; }
.csb-sug input[aria-expanded="true"] { border-radius: 10px 10px 0 0; border-bottom-color: transparent; }
.csb-sug-list {
  position: absolute; top: 100%; left: 0; right: 0;
  margin: 0; padding: 4px;
  list-style: none;
  background: #1a1a28;
  border: 1px solid #7c6cff; border-top: 0;
  border-radius: 0 0 10px 10px;
  z-index: 10;
  max-height: 220px; overflow-y: auto;
}
.csb-sug-list li {
  padding: 8px 10px;
  font: 500 13px/1.2 system-ui, sans-serif;
  color: #cbd5e1; cursor: pointer;
  border-radius: 6px;
}
.csb-sug-list li[aria-selected="true"], .csb-sug-list li:hover {
  background: rgba(124,108,255,0.12); color: #fff;
}

.csb-sr {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

document.querySelectorAll('.csb-sug').forEach(function(form) {
  var input = form.querySelector('input');
  var list  = form.querySelector('.csb-sug-list');
  var items = Array.from(list.querySelectorAll('li'));
  var idx = -1;
  function open()  { list.hidden = false; input.setAttribute('aria-expanded', 'true'); }
  function close() { list.hidden = true;  input.setAttribute('aria-expanded', 'false'); idx = -1; items.forEach(function(li){ li.removeAttribute('aria-selected'); }); }
  function filter(q) {
    var any = false;
    items.forEach(function(li) {
      var match = !q || li.textContent.toLowerCase().includes(q.toLowerCase());
      li.style.display = match ? '' : 'none';
      if (match) any = true;
    });
    return any;
  }
  function select(n) {
    items.forEach(function(li){ li.removeAttribute('aria-selected'); });
    var visible = items.filter(function(li){ return li.style.display !== 'none'; });
    if (visible.length === 0) return;
    idx = (n + visible.length) % visible.length;
    visible[idx].setAttribute('aria-selected', 'true');
  }
  input.addEventListener('focus',  function() { if (filter(input.value)) open(); });
  input.addEventListener('input',  function() { if (filter(input.value)) open(); else close(); });
  input.addEventListener('blur',   function() { setTimeout(close, 150); });
  input.addEventListener('keydown', function(e) {
    if (list.hidden) return;
    if (e.key === 'ArrowDown') { e.preventDefault(); select(idx + 1); }
    else if (e.key === 'ArrowUp') { e.preventDefault(); select(idx - 1); }
    else if (e.key === 'Escape')  { close(); input.blur(); }
    else if (e.key === 'Enter')   {
      var visible = items.filter(function(li){ return li.style.display !== 'none'; });
      if (idx >= 0 && visible[idx]) { e.preventDefault(); input.value = visible[idx].textContent; close(); }
    }
  });
  list.addEventListener('mousedown', function(e) {
    var li = e.target.closest('li[role="option"]');
    if (li) { input.value = li.textContent; close(); }
  });
});