:root{--primary: #4f7cff;--text: #222;--muted: #888;--border: #e5e5e5;--bg: #f7f8fa}*{box-sizing:border-box}body{margin:0;font-family:-apple-system,PingFang SC,Microsoft YaHei,sans-serif;color:var(--text);background:var(--bg)}a{color:var(--primary);text-decoration:none}a:hover{text-decoration:underline}.app-card{max-width:420px;margin:60px auto;padding:32px 28px;background:#fff;border-radius:12px;box-shadow:0 4px 24px #0000000f}.app-card h2{margin:0 0 24px;font-size:20px;text-align:center}.field{margin-bottom:16px}.field label{display:block;margin-bottom:6px;font-size:14px;color:var(--muted)}.field input{width:100%;padding:10px 12px;font-size:14px;border:1px solid var(--border);border-radius:6px;outline:none}.field input:focus{border-color:var(--primary)}.btn{width:100%;padding:11px;font-size:15px;color:#fff;background:var(--primary);border:none;border-radius:6px;cursor:pointer}.btn:disabled{opacity:.6;cursor:not-allowed}.btn.secondary{background:#fff;color:var(--primary);border:1px solid var(--primary)}.alert{padding:10px 12px;margin-bottom:16px;border-radius:6px;font-size:13px}.alert.error{background:#fff0f0;color:#d33}.alert.success{background:#f0fff4;color:#2c8a4a}.hint{text-align:center;margin-top:12px;font-size:13px;color:var(--muted)}