:root{--bg:#f5f7fa}
body{background:var(--bg)}
.main{min-height:calc(100vh - 200px)}
.navbtn{border:1px solid #ced4da;background:#fff;color:#495057;text-decoration:none;border-radius:3px}
.navbtn.ans{background:#198754;border-color:#198754;color:#fff}
.navbtn.marked{background:#ffc107;border-color:#ffc107;color:#212529}
.navbtn.cur{outline:2px solid #0d6efd;outline-offset:1px}
.navbtn:hover{filter:brightness(.93)}
.opt:hover{background:#f1f3f5;border-radius:6px}