body{font-family:Arial,sans-serif;text-align:center;padding:50px;background-color:#f4f4f4}#datetime-picker{padding:8px 12px;font-size:16px}button[data-start]{padding:8px 16px;font-size:16px;margin-left:10px;cursor:pointer}.timer{display:flex;justify-content:center;margin-top:30px;gap:20px}.field{background:#fff;border-radius:8px;padding:15px;box-shadow:0 0 5px #0000001a}.value{display:block;font-size:36px;font-weight:700;color:#333}.label{text-transform:uppercase;font-size:14px;color:#888}button:disabled{opacity:.6;cursor:not-allowed}