*{box-sizing:border-box}
html,body{height:100%;margin:0}
body{font-family:-apple-system,"Segoe UI",Roboto,"PingFang SC","Microsoft YaHei",sans-serif;background:linear-gradient(135deg,#1f2937,#111827);display:flex;align-items:center;justify-content:center;color:#111}
.box{background:#fff;border-radius:12px;padding:32px 28px;width:min(360px,90vw);box-shadow:0 20px 60px rgba(0,0,0,.35)}
.box h2{margin:0 0 6px;font-size:18px}
.box p.sub{margin:0 0 22px;color:#6b7280;font-size:13px}
.box input{width:100%;padding:10px 12px;border:1px solid #d1d5db;border-radius:8px;font-size:14px;outline:none}
.box input:focus{border-color:#2563eb}
.box button{width:100%;margin-top:14px;padding:10px 12px;border:none;border-radius:8px;background:#2563eb;color:#fff;font-size:14px;font-weight:600;cursor:pointer}
.box button:hover{background:#1d4ed8}
.msg{margin-top:12px;min-height:18px;font-size:13px;color:#dc2626}