:root{--pri:#1a5276;--acc:#c0392b;--bg:#fffef9;--card:#fff;--border:#e0d8c8;--form:#f0f4ff;--ex:#fffbf0;--tip:#e8f5e9;--warn:#fff3e0;--note:#f3e5f5;}
*{margin:0;padding:0;box-sizing:border-box;}
body{font-family:'Segoe UI','Microsoft YaHei',sans-serif;background:var(--bg);color:#333;line-height:1.9;padding:20px;max-width:1000px;margin:0 auto;}
h1{text-align:center;color:var(--pri);font-size:1.8em;margin:20px 0;border-bottom:3px solid var(--pri);padding-bottom:10px;}
h2{color:#fff;font-size:1.4em;margin:35px 0 15px;padding:10px 18px;background:linear-gradient(135deg,var(--pri),#2980b9);border-radius:6px;}
h3{color:var(--pri);font-size:1.15em;margin:20px 0 10px;border-left:4px solid var(--acc);padding-left:12px;}
h4{color:#555;margin:12px 0 6px;font-size:1.05em;}
.card{background:var(--card);border:1px solid var(--border);border-radius:8px;padding:18px;margin:14px 0;}
.fb{background:var(--form);border:2px solid #3498db;border-radius:8px;padding:14px 18px;margin:12px 0;}
.fb .t{font-weight:bold;color:#2471a3;margin-bottom:6px;}
.ex{background:var(--ex);border-left:4px solid #f39c12;border-radius:0 8px 8px 0;padding:14px 18px;margin:12px 0;}
.sol{background:#f5f5f5;border:1px dashed #aaa;border-radius:5px;padding:14px;margin-top:8px;}
.sol .st{font-weight:bold;color:var(--acc);margin-bottom:4px;}
.tip{background:var(--tip);border-left:4px solid #27ae60;border-radius:0 8px 8px 0;padding:10px 16px;margin:10px 0;}
.warn{background:var(--warn);border-left:4px solid #e67e22;border-radius:0 8px 8px 0;padding:10px 16px;margin:10px 0;}
.note{background:var(--note);border-left:4px solid #8e24aa;border-radius:0 8px 8px 0;padding:10px 16px;margin:10px 0;}
table{width:100%;border-collapse:collapse;margin:12px 0;}
th,td{border:1px solid var(--border);padding:6px 10px;text-align:center;}
th{background:var(--pri);color:#fff;}
tr:nth-child(even){background:#f9f7f2;}
details{margin:8px 0;}
details summary{cursor:pointer;font-weight:bold;color:var(--pri);padding:4px;}
ul,ol{margin-left:20px;margin-bottom:8px;}
.nav-bar{position:sticky;top:0;z-index:100;background:#fffef9;padding:10px 15px;border-bottom:2px solid #e0d8c8;margin:-20px -20px 20px;font-size:.9em;display:flex;gap:12px;flex-wrap:wrap;}
.nav-bar a{color:#1a5276;text-decoration:none;font-weight:bold;padding:3px 8px;border-radius:4px;}
.nav-bar a:hover{background:#1a5276;color:#fff;}
.page-ref{font-size:.8em;color:#aaa;float:right;}
figure.plot{margin:14px 0;text-align:center;}
figure.plot img{max-width:100%;height:auto;border:1px solid var(--border);border-radius:8px;background:#fff;}
figure.plot figcaption{font-size:.85em;color:#888;margin-top:6px;}
@media print {
  .nav-bar, #floating-toc, #back-to-top, #reading-progress-top, script { display: none !important; }
  body { max-width: none; padding: 10mm; font-size: 10pt; line-height: 1.5; background: #fff; }
  h1, h2, h3, h4 { page-break-after: avoid; }
  .ex, .card, .fb { page-break-inside: avoid; }
  h1 { font-size: 18pt; }
  h2 { font-size: 14pt; background: #eee !important; color: #000 !important; -webkit-print-color-adjust: exact; }
  h3 { font-size: 12pt; }
  .banner { background: #f0f0f0 !important; color: #000 !important; border: 1px solid #999; -webkit-print-color-adjust: exact; }
  .fb, .ex, .tip, .warn, .note { border: 1px solid #ccc; background: #fafafa !important; -webkit-print-color-adjust: exact; }
  a { color: #000; text-decoration: none; }
  details summary { font-weight: bold; }
  details[open] summary::after { content: ""; }
}