*{box-sizing:border-box;margin:0;padding:0}body{color:#222;background:#f5f7fa;padding:40px;font-family:system-ui,-apple-system,Segoe UI,Roboto,sans-serif}header{margin-bottom:50px}hr{margin-top:200px}input{box-sizing:border-box;border:1px solid #ccc;border-radius:5px;width:100%;padding:10px;font-size:16px;transition:border-color .3s}#btn{color:#fff;cursor:pointer;background-color:#5e5c64;border:none;border-radius:8px;padding:12px 24px;font-size:1rem;font-weight:600;transition:all .3s}#output{margin-top:50px}