*{box-sizing:border-box} body{margin:0;font:16px/1.5 system-ui,Arial}
.topnav{display:flex;gap:16px;align-items:center;padding:14px 20px;border-bottom:1px solid #eee}
.topnav a{text-decoration:none;color:#333;padding:6px 10px;border-radius:8px}
.topnav a.active,.topnav a:hover{background:#f2f2f2}
.container{max-width:980px;margin:32px auto;padding:0 16px}
.site-footer{margin-top:48px;padding:24px 16px;border-top:1px solid #eee;text-align:center;color:#666}
.btn{display:inline-block;padding:10px 16px;border:1px solid #222;border-radius:10px;background:#fff;cursor:pointer}
.btn:hover{background:#f7f7f7}
input,textarea{width:100%;padding:10px;border:1px solid #ddd;border-radius:8px}
label{display:block;margin:12px 0 6px}
form{display:grid;gap:12px;max-width:620px}
.alert{padding:12px;border-radius:8px}
.alert.ok{background:#e8f6ee;border:1px solid #bde5c8;color:#276749}
.alert.err{background:#ffecec;border:1px solid #f5aca6;color:#a33}