.acc { max-width: 1100px; margin: 20px auto; font-family: system-ui, Arial, sans-serif; }
  details { border: 1px solid #ddd; margin-bottom: 10px; }
  summary {
    cursor: pointer;
    padding: 12px 16px;
    font-weight: 700;
    font-size: 18px;
    background: #f7f7f7;
  }
  summary::marker { content: ""; }  /* hide default arrow */
  summary::before {
    content: "+ ";
    font-weight: 900;
    margin-right: 6px;
  }
  details[open] summary::before {
    content: "- ";
    color: green;
  }

  .conference-row {
    padding: 8px 16px;
    border-bottom: 1px solid #eee;
    font-size: 15px;
  }
  .conference-row:last-child { border-bottom: none; }