:root{
  --bg:#f7f8fa; --card:#fff; --fg:#1a2233; --muted:#6b7484; --line:#e6e9ef;
  --primary:#2563eb; --primary-d:#1d4ed8; --accent:#f0f4ff; --radius:12px;
  --shadow:0 1px 2px rgba(16,24,40,.06),0 1px 3px rgba(16,24,40,.1);
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  color:var(--fg);background:var(--bg);line-height:1.65;font-size:15px}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:1080px;margin:0 auto;padding:0 16px}
.site-header{background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}
.site-header .wrap{display:flex;align-items:center;gap:16px;height:58px;flex-wrap:wrap}
.logo{font-weight:700;font-size:18px;color:var(--fg)}
.topnav{display:flex;gap:14px;flex-wrap:wrap;font-size:14px}
.topnav a{color:var(--muted);white-space:nowrap}
.topnav a:hover{color:var(--primary)}
main.wrap{padding-top:24px;padding-bottom:56px;min-height:60vh}
.hero{background:linear-gradient(135deg,#eef4ff,#f8fbff);border:1px solid var(--line);border-radius:var(--radius);padding:32px 24px;margin-bottom:28px}
.hero h1{margin:0 0 10px;font-size:26px;line-height:1.3}
.lede{color:var(--muted);margin:0 0 6px;font-size:15px}
.lede strong{color:var(--primary-d)}
.searchbar{display:flex;gap:8px;margin-top:16px;max-width:560px}
.searchbar input{flex:1;padding:11px 14px;border:1px solid var(--line);border-radius:10px;font-size:15px;background:#fff}
.searchbar input:focus{outline:none;border-color:var(--primary)}
.searchbar button{padding:11px 20px;border:0;border-radius:10px;background:var(--primary);color:#fff;font-size:15px;cursor:pointer}
.searchbar button:hover{background:var(--primary-d)}
h2{font-size:19px;margin:30px 0 14px;padding-left:11px;border-left:4px solid var(--primary)}
h1{font-size:24px;margin:8px 0 10px;line-height:1.3}
.chips{display:flex;flex-wrap:wrap;gap:10px;margin:8px 0 4px}
.chip{background:#fff;border:1px solid var(--line);border-radius:999px;padding:7px 14px;font-size:14px;color:var(--fg)}
.chip:hover{border-color:var(--primary);text-decoration:none}
.chip b{color:var(--muted);font-weight:500;margin-left:2px}
.grid{display:grid;gap:14px}
.cards{grid-template-columns:repeat(auto-fill,minmax(220px,1fr))}
.btns-grid{grid-template-columns:repeat(auto-fill,minmax(140px,1fr))}
.big-btn{display:flex;flex-direction:column;align-items:center;gap:2px;background:#fff;border:1px solid var(--line);
  border-radius:var(--radius);padding:18px 12px;font-weight:600;font-size:16px;color:var(--fg);box-shadow:var(--shadow)}
.big-btn span{font-size:12px;color:var(--muted);font-weight:400}
.big-btn:hover{border-color:var(--primary);text-decoration:none;transform:translateY(-1px);transition:.15s}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:14px;box-shadow:var(--shadow);display:flex;flex-direction:column;gap:8px}
.card-title{font-weight:600;color:var(--fg);font-size:15px;line-height:1.4}
.card-title:hover{color:var(--primary)}
.meta{font-size:12.5px;color:var(--muted)}
.btn{display:inline-block;text-align:center;background:var(--primary);color:#fff;border-radius:9px;padding:9px 16px;font-size:14px;font-weight:500}
.btn:hover{background:var(--primary-d);text-decoration:none;color:#fff}
.btn.big{font-size:16px;padding:14px 26px;border-radius:11px}
.btn.disabled{background:#c9ced8;cursor:default}
.crumbs{font-size:13px;color:var(--muted);margin-bottom:12px;line-height:1.9}
.crumbs a{color:var(--muted)}
.crumbs span{color:var(--fg)}
.book-detail{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:var(--shadow)}
.book-meta{display:flex;flex-wrap:wrap;gap:8px 16px;font-size:13.5px;color:var(--muted);margin:14px 0}
.book-meta span{background:var(--accent);border-radius:8px;padding:4px 10px;color:var(--primary-d)}
.download-box{margin:22px 0;text-align:center;background:linear-gradient(135deg,#f5f9ff,#fbfdff);border:1px dashed #c7d8ff;border-radius:var(--radius);padding:26px 16px}
.note{font-size:13px;color:var(--muted);margin:10px 0 0}
.desc{margin-top:26px}
.desc p{color:#3a4256}
.hint{color:var(--muted);font-size:13.5px}
.site-footer{border-top:1px solid var(--line);background:#fff;padding:24px 0;margin-top:40px}
.site-footer p{margin:4px 0;font-size:13px;color:var(--muted)}
/* covers */
.cover{display:block;width:100%;border-radius:8px;background:#f4f6f9;object-fit:contain}
.cover.sm{aspect-ratio:4/5;max-height:240px}
.cover.ph{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:4px;aspect-ratio:3/4;background:linear-gradient(150deg,var(--c),#0b1b3a);color:#fff;font-style:normal;text-align:center;padding:10px}
.cover.ph b{font-size:20px}
.cover.ph span{font-size:13px;opacity:.9}
.cover.ph i{font-size:12px;opacity:.75;font-style:normal}
.cover.ph.sm{max-height:210px}
.card .cover{margin-bottom:2px}
/* book top */
.book-top{display:flex;gap:22px;flex-wrap:wrap}
.book-cover{flex:0 0 auto}
.book-head{flex:1;min-width:260px}
.book-detail .download-box{text-align:left;padding:16px 18px;margin:16px 0}
/* toc */
.sec{margin-top:26px}
.toc{list-style:none;padding:0;margin:0;border:1px solid var(--line);border-radius:10px;overflow:hidden}
.toc li{display:flex;justify-content:space-between;gap:12px;padding:8px 14px;border-bottom:1px solid var(--line);font-size:14px}
.toc li:last-child{border-bottom:0}
.toc li.toc-h{background:var(--accent);font-weight:600;color:var(--primary-d)}
.toc li em{color:var(--muted);font-style:normal}
.toc-raw{white-space:pre-wrap;background:#f9fafc;border:1px solid var(--line);border-radius:10px;padding:14px;font-size:13px;color:#3a4256;max-height:340px;overflow:auto}
.cover.big{width:220px;max-width:100%;aspect-ratio:4/5}
/* preview viewer */
.pv-viewer{position:relative;background:#0f1522;border-radius:12px;overflow:hidden;display:flex;align-items:center;justify-content:center;min-height:320px;padding:14px;max-width:820px;margin:0 auto}
.pv-main{max-width:100%;max-height:70vh;object-fit:contain;cursor:zoom-in;border-radius:4px;background:#fff}
.pv-nav{position:absolute;top:50%;transform:translateY(-50%);width:44px;height:44px;border:0;border-radius:50%;background:rgba(255,255,255,.85);color:#111;font-size:26px;line-height:1;cursor:pointer;z-index:3;display:flex;align-items:center;justify-content:center}
.pv-nav:hover{background:#fff}
.pv-prev{left:10px}.pv-next{right:10px}
.pv-bar{position:absolute;bottom:10px;left:0;right:0;display:flex;justify-content:space-between;padding:0 16px;color:#cfd6e4;font-size:13px;pointer-events:none}
.pv-thumbs{display:flex;gap:8px;margin-top:10px;overflow-x:auto;padding-bottom:4px}
.pv-thumb{width:54px;height:72px;object-fit:contain;background:#fff;border:2px solid transparent;border-radius:5px;cursor:pointer;flex:0 0 auto}
.pv-thumb.on{border-color:var(--primary)}
/* lightbox */
.pv-lb{position:fixed;inset:0;background:rgba(0,0,0,.92);z-index:9999;display:none;align-items:center;justify-content:center}
.pv-lb.on{display:flex}
.pv-lb img{max-width:96vw;max-height:96vh;object-fit:contain;cursor:zoom-out}
.pv-lb .pv-nav{width:52px;height:52px;font-size:30px}
.pv-lb .pv-close{position:absolute;top:16px;right:18px;color:#fff;font-size:34px;cursor:pointer;z-index:2;line-height:1}
@media(max-width:640px){.pv-main{max-height:56vh}}
/* filters */
.filters{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:16px;box-shadow:var(--shadow);margin-bottom:20px}
.fgroup{display:flex;gap:12px;padding:8px 0;border-bottom:1px dashed var(--line);align-items:flex-start}
.fgroup label{flex:0 0 48px;color:var(--muted);font-size:14px;padding-top:5px}
.fchips{display:flex;flex-wrap:wrap;gap:8px}
.fchip{border:1px solid var(--line);background:#fff;border-radius:999px;padding:5px 12px;font-size:13px;cursor:pointer;color:var(--fg)}
.fchip:hover{border-color:var(--primary)}
.fchip.on{background:var(--primary);color:#fff;border-color:var(--primary)}
.fbar{display:flex;justify-content:space-between;align-items:center;padding-top:12px;color:var(--muted);font-size:14px}
/* faq */
.faq{display:grid;gap:10px}
.faq details{border:1px solid var(--line);border-radius:10px;padding:10px 14px;background:#fff}
.faq summary{cursor:pointer;font-weight:600;color:var(--fg)}
.faq p{margin:8px 0 0;color:var(--muted);font-size:14px}
@media(max-width:640px){
  .hero{padding:22px 16px}.hero h1{font-size:21px}
  .topnav{gap:10px;font-size:13px;overflow-x:auto;padding-bottom:2px}
  .book-detail{padding:16px}
  main.wrap{padding-top:16px}
}