Le menu qui se ferme tout seul

Version ratée

<button id="toggle-bad">Menu</button>
<ul id="menu-bad" hidden>
  <li><a href="#">Tarifs</a></li>
</ul>

Version corrigée

<button id="toggle-good" aria-expanded="false" aria-controls="menu-good">Menu</button>
<ul id="menu-good" hidden>
  <li><a href="#">Tarifs</a></li>
</ul>

.demo-submenu {
  list-style: none;
  margin: 0;
  padding: 0.5rem 0;
}

.demo-submenu li {
  padding: 0.4rem 0.75rem;
  border-radius: 0.35rem;
}

.demo-submenu li:hover {
  background: rgba(255, 172, 51, 0.1);
}

.demo-submenu li:focus-within {
  outline: 2px solid var(--c-ambre);
}