details { border-bottom: 1px solid #ddd; padding: 16px 0; }
summary { list-style: none; cursor: pointer; display: flex; justify-content: space-between; align-items: center; font-size: 1.1em; }
summary::-webkit-details-marker { display: none; }
summary::after { content: "+"; font-size: 1.2em; }
details[open] summary::after { content: "×"; }
details p { margin: 12px 0 0 0; }