/* ============================================================
   电路分析 · 复习台  —  stylesheet
   ============================================================ */
:root{
  --paper:#f6f4ef;
  --paper-2:#efedE6;
  --card:#fffefb;
  --ink:#191c1f;
  --ink-2:#3d444b;
  --muted:#7c848c;
  --line:#e4e0d6;
  --line-2:#efece4;
  --accent:#17594f;
  --accent-2:#0f766e;
  --accent-soft:#e6efec;
  --amber:#a86400;
  --amber-soft:#fbf1dd;
  --red:#a93a2f;
  --red-soft:#fbeae7;
  --blue:#2a5db0;
  --blue-soft:#e9eff9;
  --ok:#2f7d54;
  --radius:14px;
  --shadow:0 1px 2px rgba(24,28,32,.04), 0 8px 24px -12px rgba(24,28,32,.18);
  --shadow-lg:0 2px 6px rgba(24,28,32,.06), 0 24px 60px -24px rgba(24,28,32,.35);
  --mono:"Cascadia Mono","Consolas",ui-monospace,monospace;
  --sans:"Segoe UI","Microsoft YaHei UI","Microsoft YaHei",system-ui,-apple-system,sans-serif;
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  font-size:15px;
  line-height:1.68;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
a{color:inherit;text-decoration:none}
button{font-family:inherit;font-size:inherit;cursor:pointer}
::selection{background:#cfe3dd}

/* ---------- top bar ---------- */
.topbar{
  position:sticky;top:0;z-index:50;
  display:flex;align-items:center;gap:18px;
  height:58px;padding:0 22px;
  background:rgba(246,244,239,.88);
  backdrop-filter:blur(12px) saturate(1.2);
  border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:10px;flex:0 0 auto}
.brand-mark{
  width:32px;height:32px;border-radius:9px;
  background:linear-gradient(150deg,#1b6a5e,#0e3f38);
  color:#eaf3f0;display:grid;place-items:center;
  font-size:18px;font-weight:600;letter-spacing:0;
  box-shadow:inset 0 1px 0 rgba(255,255,255,.25), 0 4px 10px -4px rgba(14,63,56,.6);
}
.brand-text{display:flex;flex-direction:column;line-height:1.15}
.brand-text b{font-size:14.5px;letter-spacing:.02em}
.brand-text i{font-style:normal;font-size:10.5px;color:var(--muted);letter-spacing:.09em;text-transform:uppercase}

.nav{display:flex;gap:2px;margin-left:8px;flex-wrap:wrap}
.nav a{
  padding:6px 11px;border-radius:8px;font-size:13.5px;color:var(--ink-2);
  transition:background .15s,color .15s;
}
.nav a:hover{background:rgba(23,89,79,.07);color:var(--accent)}
.nav a.active{background:var(--accent);color:#fff;box-shadow:0 4px 12px -6px rgba(23,89,79,.8)}

.search-btn{
  margin-left:auto;display:flex;align-items:center;gap:7px;
  padding:6px 10px;border:1px solid var(--line);border-radius:9px;
  background:var(--card);color:var(--muted);font-size:13px;
  transition:border-color .15s, box-shadow .15s;
}
.search-btn:hover{border-color:#cfd8d4;box-shadow:var(--shadow)}
.search-btn kbd{
  font-family:var(--mono);font-size:10.5px;padding:1px 5px;border-radius:4px;
  background:var(--paper-2);border:1px solid var(--line);color:var(--muted);
}

/* ---------- layout ---------- */
main{padding:26px 22px 90px;max-width:1400px;margin:0 auto}
.view-head{margin:0 0 22px}
.view-head h1{font-size:23px;margin:0 0 5px;letter-spacing:.01em}
.view-head p{margin:0;color:var(--muted);font-size:13.5px}

/* ---------- home ---------- */
.hero{
  position:relative;overflow:hidden;
  background:linear-gradient(140deg,#123f39 0%,#17594f 46%,#1d6f61 100%);
  color:#eef5f2;border-radius:20px;padding:34px 36px 30px;
  box-shadow:0 24px 50px -30px rgba(15,63,56,.9);
}
.hero::after{
  content:"";position:absolute;inset:0;
  background-image:radial-gradient(circle at 88% 18%,rgba(255,255,255,.14),transparent 42%),
                   repeating-linear-gradient(115deg,rgba(255,255,255,.045) 0 1px,transparent 1px 26px);
  pointer-events:none;
}
.hero h1{margin:0 0 8px;font-size:31px;letter-spacing:.02em;font-weight:650}
.hero h1 small{font-size:13px;font-weight:400;opacity:.62;letter-spacing:.14em;display:block;margin-top:8px;text-transform:uppercase}
.hero p{margin:0;max-width:660px;font-size:14px;line-height:1.75;color:rgba(238,245,242,.82)}
.hero-kpis{display:flex;gap:30px;margin-top:24px;flex-wrap:wrap;position:relative}
.hero-kpi b{display:block;font-size:25px;line-height:1.15;letter-spacing:.01em}
.hero-kpi span{font-size:11.5px;opacity:.66;letter-spacing:.09em}

.course-strip{
  display:grid;grid-template-columns:repeat(auto-fit,minmax(252px,1fr));gap:16px;margin:18px 0 30px;
}
.strip-card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:16px 18px;box-shadow:var(--shadow);position:relative;overflow:hidden;
}
.strip-card h3{margin:0 0 10px;font-size:12px;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);font-weight:600}
.strip-card .big{font-size:14.5px;line-height:1.7}
.strip-card .big b{color:var(--accent)}

.grade-bar{display:flex;height:9px;border-radius:99px;overflow:hidden;margin:11px 0 9px;background:var(--paper-2)}
.grade-bar i{display:block;height:100%}
.grade-legend{display:flex;gap:14px;flex-wrap:wrap;font-size:12px;color:var(--ink-2)}
.grade-legend i{display:inline-block;width:8px;height:8px;border-radius:2px;margin-right:5px}

.gap-card{
  border:1px solid #e8d9b6;background:linear-gradient(180deg,#fdf8ec,#fbf4e4);
  border-radius:var(--radius);padding:18px 20px;margin:0 0 30px;
}
.gap-card h3{margin:0 0 8px;font-size:14px;color:#7a4a00;display:flex;align-items:center;gap:8px}
.gap-card p{margin:0 0 10px;font-size:13.5px;color:#6b4a12;line-height:1.7}
.gap-card ul{margin:0;padding-left:18px;columns:2;column-gap:26px;font-size:13px;color:#6b4a12}
.gap-card li{margin:3px 0;break-inside:avoid}

.unit{margin:0 0 34px}
.unit-head{display:flex;align-items:baseline;gap:12px;margin:0 0 14px;padding-bottom:9px;border-bottom:1px solid var(--line)}
.unit-idx{
  font-family:var(--mono);font-size:12px;font-weight:700;color:#fff;background:var(--accent);
  width:22px;height:22px;border-radius:6px;display:grid;place-items:center;flex:0 0 auto;
  transform:translateY(1px);
}
.unit-head h2{font-size:16.5px;margin:0;font-weight:650;letter-spacing:.01em}
.unit-head span{font-size:12.5px;color:var(--muted)}

.ch-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(292px,1fr));gap:14px}
.ch-card{
  display:flex;flex-direction:column;gap:9px;
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:15px 16px 13px;box-shadow:var(--shadow);
  transition:transform .18s cubic-bezier(.2,.8,.3,1), box-shadow .18s, border-color .18s;
}
.ch-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg);border-color:#d5ddd8}
.ch-card .no{font-family:var(--mono);font-size:11px;color:var(--muted);letter-spacing:.06em}
.ch-card h3{margin:0;font-size:16px;font-weight:650;letter-spacing:.01em}
.ch-card .en{font-size:11.5px;color:var(--muted);letter-spacing:.02em;margin-top:-6px}
.ch-card .blurb{font-size:12.8px;color:var(--ink-2);line-height:1.62;flex:1}
.ch-card .meta{display:flex;gap:12px;font-size:11.5px;color:var(--muted);align-items:center}
.ch-card .meta b{color:var(--ink-2);font-weight:600}
.mini-bar{height:4px;border-radius:99px;background:var(--paper-2);overflow:hidden;margin-top:2px}
.mini-bar i{display:block;height:100%;background:linear-gradient(90deg,#2b8a76,#17594f);border-radius:99px;transition:width .3s}

/* ---------- reader ---------- */
.reader{display:flex;flex-direction:column;gap:12px}
.reader-top{display:flex;align-items:center;gap:14px;flex-wrap:wrap}
.reader-top .back{font-size:13px;color:var(--muted)}
.reader-top .back:hover{color:var(--accent)}
.reader-title{font-size:15px;font-weight:650}
.reader-title em{font-style:normal;color:var(--muted);font-weight:400;font-size:12.5px;margin-left:8px}
.reader-top .spacer{flex:1}
.pager{display:flex;align-items:center;gap:6px;font-size:12.5px;color:var(--muted)}
.pager input{
  width:44px;padding:3px 6px;border:1px solid var(--line);border-radius:6px;
  background:var(--card);text-align:center;font-family:var(--mono);font-size:12px;color:var(--ink);
}

.reader-body{display:grid;grid-template-columns:minmax(0,1fr) 424px;gap:14px;align-items:start}
.stage-wrap{
  background:#1a1d20;border-radius:var(--radius);overflow:hidden;position:relative;
  box-shadow:var(--shadow);display:flex;align-items:center;justify-content:center;
  min-height:340px;
}
.stage-wrap img{
  display:block;cursor:zoom-in;width:auto;height:auto;
  max-width:100%;max-height:calc(100vh - 252px);
  margin:auto;
}
.stage-nav{
  position:absolute;top:50%;transform:translateY(-50%);
  width:38px;height:56px;display:grid;place-items:center;
  background:rgba(16,19,21,.55);color:#fff;border:0;font-size:22px;line-height:1;
  opacity:0;transition:opacity .18s;backdrop-filter:blur(4px);
}
.stage-wrap:hover .stage-nav{opacity:1}
.stage-nav.prev{left:0;border-radius:0 8px 8px 0}
.stage-nav.next{right:0;border-radius:8px 0 0 8px}
.stage-nav:hover{background:rgba(16,19,21,.8)}

.panel{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);display:flex;flex-direction:column;
  max-height:calc(100vh - 150px);position:sticky;top:72px;
}
.panel-head{padding:13px 16px 11px;border-bottom:1px solid var(--line-2);display:flex;align-items:center;gap:9px;flex-wrap:wrap}
.panel-head .pno{font-family:var(--mono);font-size:11px;color:#fff;background:var(--ink-2);padding:2px 7px;border-radius:5px}
.kind{font-size:10.5px;letter-spacing:.06em;padding:2px 7px;border-radius:5px;background:var(--paper-2);color:var(--muted);border:1px solid var(--line-2)}
.kind.example{background:var(--amber-soft);color:#7a4a00;border-color:#f0e0bf}
.kind.quiz{background:var(--blue-soft);color:var(--blue);border-color:#dce6f7}
.kind.formula{background:var(--accent-soft);color:var(--accent);border-color:#d7e6e1}
.lang-toggle{margin-left:auto;display:flex;background:var(--paper-2);border-radius:8px;padding:2px}
.lang-toggle button{border:0;background:transparent;padding:3px 9px;border-radius:6px;font-size:11.5px;color:var(--muted)}
.lang-toggle button.on{background:var(--card);color:var(--ink);box-shadow:0 1px 3px rgba(0,0,0,.09)}

.panel-body{padding:14px 16px 18px;overflow:auto;flex:1}
.panel-body h4{margin:0 0 7px;font-size:17px;line-height:1.4;letter-spacing:.01em}
.gist{
  font-size:13.2px;line-height:1.75;color:var(--ink-2);
  background:linear-gradient(180deg,#f8f7f3,#f4f3ee);
  border-left:3px solid var(--accent);border-radius:0 8px 8px 0;
  padding:9px 12px;margin:0 0 14px;
}
.panel h5{
  font-size:11px;letter-spacing:.13em;text-transform:uppercase;color:var(--muted);
  margin:16px 0 8px;font-weight:600;display:flex;align-items:center;gap:8px;
}
.panel h5::after{content:"";flex:1;height:1px;background:var(--line-2)}

.bullet{display:grid;gap:2px;padding:7px 0;border-bottom:1px dashed var(--line-2)}
.bullet:last-child{border-bottom:0}
.bullet .en{font-size:12px;color:#767f87;line-height:1.62;letter-spacing:.005em}
.bullet .zh{font-size:13.2px;color:var(--ink-2);line-height:1.7}
body.lang-zh .bullet .en{display:none}
body.lang-zh .bullet{padding:6px 0}

.ex-box{border:1px solid #eadfc6;background:#fdfaf2;border-radius:10px;padding:12px 13px;margin:12px 0 2px}
.ex-box .tag{font-size:10.5px;letter-spacing:.1em;color:#7a4a00;font-weight:700;text-transform:uppercase}
.ex-box .problem{font-size:13.2px;margin:6px 0 8px;line-height:1.7}
.ex-given{font-size:12.5px;color:var(--ink-2);background:#fff;border:1px dashed #e6d9bd;border-radius:7px;padding:6px 9px;margin:8px 0;font-family:var(--mono);line-height:1.6}
.ex-steps{margin:8px 0;padding-left:0;list-style:none;counter-reset:st}
.ex-steps li{counter-increment:st;position:relative;padding-left:25px;margin:6px 0;font-size:13px;line-height:1.7;color:var(--ink-2)}
.ex-steps li::before{
  content:counter(st);position:absolute;left:0;top:3px;
  width:17px;height:17px;border-radius:5px;background:var(--accent);color:#fff;
  font-size:10.5px;display:grid;place-items:center;font-family:var(--mono);
}
.ex-answer{
  margin-top:10px;padding:8px 11px;border-radius:8px;
  background:#eaf3ef;border:1px solid #cfe3da;color:#124c42;
  font-size:13px;font-weight:600;
}

.terms{display:flex;flex-wrap:wrap;gap:6px}
.term-chip{
  font-size:11.5px;padding:3px 9px;border-radius:99px;
  background:var(--paper-2);border:1px solid var(--line);color:var(--ink-2);
}
.term-chip b{font-weight:600;color:var(--accent)}

.status-bar{display:flex;gap:6px;padding:10px 16px;border-top:1px solid var(--line-2);background:#fbfaf6;border-radius:0 0 var(--radius) var(--radius)}
.st-btn{
  flex:1;border:1px solid var(--line);background:var(--card);border-radius:8px;
  padding:6px 4px;font-size:11.5px;color:var(--ink-2);transition:.15s;
}
.st-btn:hover{border-color:#c9d3cf}
.st-btn.on[data-s="1"]{background:#e6f2ec;border-color:#9ecdb9;color:#1c6b4b;font-weight:600}
.st-btn.on[data-s="2"]{background:var(--amber-soft);border-color:#e8cf9a;color:#7a4a00;font-weight:600}
.st-btn.on[data-s="3"]{background:var(--red-soft);border-color:#e8b6ae;color:var(--red);font-weight:600}

.thumbs{display:flex;gap:7px;overflow-x:auto;padding:4px 2px 10px;scrollbar-width:thin}
.thumb{
  flex:0 0 auto;position:relative;border-radius:7px;overflow:hidden;
  border:2px solid transparent;background:#dcd9d1;line-height:0;
  transition:border-color .15s, transform .15s;
}
.thumb img{width:96px;height:54px;object-fit:cover;display:block;opacity:.88}
.thumb:hover{transform:translateY(-2px)}
.thumb.on{border-color:var(--accent)}
.thumb.on img{opacity:1}
.thumb .dot{position:absolute;left:4px;top:4px;width:7px;height:7px;border-radius:99px;box-shadow:0 0 0 1.5px rgba(255,255,255,.85)}
.thumb .num{position:absolute;right:3px;bottom:3px;font-size:9.5px;font-family:var(--mono);color:#fff;background:rgba(20,24,26,.62);padding:0 4px;border-radius:3px;line-height:1.5}

/* ---------- generic cards / lists ---------- */
.toolbar{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin:0 0 18px}
.field{
  display:flex;align-items:center;gap:7px;padding:6px 11px;
  background:var(--card);border:1px solid var(--line);border-radius:9px;box-shadow:var(--shadow);
}
.field input{border:0;outline:0;background:transparent;font-size:13px;width:220px;color:var(--ink)}
.field svg{color:var(--muted)}
.chips{display:flex;gap:6px;flex-wrap:wrap}
.chip{
  padding:4px 11px;border-radius:99px;border:1px solid var(--line);
  background:var(--card);font-size:12.5px;color:var(--ink-2);transition:.15s;
}
.chip:hover{border-color:#c9d3cf}
.chip.on{background:var(--accent);border-color:var(--accent);color:#fff}

.point-card,.exam-card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:15px 17px;box-shadow:var(--shadow);margin:0 0 12px;
}
.point-card h4,.exam-card h4{margin:0 0 7px;font-size:15.5px;display:flex;align-items:baseline;gap:9px;flex-wrap:wrap}
.point-card .body{font-size:13.4px;color:var(--ink-2);line-height:1.75;margin:0}
.tex{
  margin:10px 0;padding:11px 13px;background:#f7f6f2;border:1px solid var(--line-2);
  border-radius:9px;overflow-x:auto;text-align:center;font-size:14px;
}
.rows{display:flex;flex-direction:column;gap:6px;margin-top:10px}
.row{display:grid;grid-template-columns:66px 1fr;gap:9px;font-size:12.8px;line-height:1.7}
.row b{color:var(--muted);font-weight:600;font-size:11px;letter-spacing:.06em;padding-top:2px}
.row.warn b{color:var(--red)}
.row.warn span{color:#7c332b}
.row.cond b{color:var(--blue)}

.refs{display:flex;gap:5px;flex-wrap:wrap;margin-top:10px;align-items:center}
.ref{
  font-family:var(--mono);font-size:11px;padding:2px 7px;border-radius:6px;
  background:var(--paper-2);border:1px solid var(--line);color:var(--ink-2);
}
.ref:hover{background:var(--accent);color:#fff;border-color:var(--accent)}
.refs span{font-size:11px;color:var(--muted);margin-right:2px}

.star{color:var(--amber);letter-spacing:.12em;font-size:12.5px}
.star .off{color:#ddd8cd}
.badge{font-size:10.5px;padding:1px 7px;border-radius:5px;background:var(--paper-2);border:1px solid var(--line);color:var(--muted);font-weight:400}
.badge.type{background:var(--blue-soft);border-color:#dbe5f6;color:var(--blue)}

.steps-ol{margin:10px 0 0;padding-left:0;list-style:none;counter-reset:tpl}
.steps-ol li{counter-increment:tpl;position:relative;padding-left:24px;margin:5px 0;font-size:13px;color:var(--ink-2);line-height:1.7}
.steps-ol li::before{
  content:counter(tpl);position:absolute;left:0;top:3px;width:17px;height:17px;border-radius:5px;
  background:var(--accent-soft);color:var(--accent);font-size:10.5px;font-weight:700;
  display:grid;place-items:center;font-family:var(--mono);
}
.basis{margin-top:9px;font-size:11.5px;color:var(--muted);border-top:1px dashed var(--line-2);padding-top:8px}

/* ---------- formula page ---------- */
.fgroup{margin:0 0 26px;break-inside:avoid}
.fgroup h3{font-size:13.5px;margin:0 0 10px;letter-spacing:.02em;display:flex;align-items:center;gap:9px}
.fgroup h3 .no{font-family:var(--mono);font-size:11px;color:#fff;background:var(--accent);padding:1px 6px;border-radius:4px}
.fgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:10px}
.fcard{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:11px 13px;box-shadow:var(--shadow)}
.fcard .name{font-size:12.5px;color:var(--ink-2);margin-bottom:4px;display:flex;gap:7px;align-items:baseline}
.fcard .name .ref{margin-left:auto}
.fcard .katex-display{margin:4px 0}
.fcard .katex{font-size:1.02em}

/* ---------- glossary ---------- */
.gtable{width:100%;border-collapse:collapse;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow)}
.gtable th{
  text-align:left;font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);
  padding:9px 14px;background:#f8f7f2;border-bottom:1px solid var(--line);font-weight:600;
}
.gtable td{padding:8px 14px;border-bottom:1px solid var(--line-2);font-size:13.2px}
.gtable tr:last-child td{border-bottom:0}
.gtable tr:hover td{background:#faf9f4}
.gtable .en{font-size:12.8px;color:var(--ink-2)}
.gtable .zh{font-weight:600}
.gtable .loc{font-family:var(--mono);font-size:11px;color:var(--muted);white-space:nowrap}

/* ---------- quiz ---------- */
.quiz-wrap{max-width:760px;margin:0 auto}
.qcard{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px 24px;box-shadow:var(--shadow)}
.qmeta{display:flex;gap:9px;align-items:center;font-size:11.5px;color:var(--muted);margin-bottom:12px}
.qtext{font-size:15px;line-height:1.8;white-space:pre-wrap;margin:0 0 16px}
.opts{display:flex;flex-direction:column;gap:8px}
.opt{
  display:flex;gap:11px;align-items:flex-start;text-align:left;
  padding:10px 13px;border:1px solid var(--line);border-radius:10px;background:#fff;
  font-size:13.5px;color:var(--ink-2);transition:.15s;line-height:1.65;
}
.opt:hover{border-color:#c9d3cf;background:#fcfbf7}
.opt .k{
  flex:0 0 20px;height:20px;border-radius:6px;background:var(--paper-2);border:1px solid var(--line);
  display:grid;place-items:center;font-family:var(--mono);font-size:11px;color:var(--muted);margin-top:1px;
}
.opt.correct{border-color:#8ec6ae;background:#eef7f2}
.opt.correct .k{background:var(--ok);color:#fff;border-color:var(--ok)}
.opt.wrong{border-color:#e2a89f;background:#fdf1ef}
.opt.wrong .k{background:var(--red);color:#fff;border-color:var(--red)}
.opt[disabled]{cursor:default}
.qfeed{margin-top:16px;padding:13px 15px;border-radius:10px;background:#f8f7f2;border:1px solid var(--line-2);font-size:13px;line-height:1.75;display:none}
.qfeed.show{display:block}
.qfeed .res{font-weight:700;margin-bottom:6px}
.qfeed .res.ok{color:var(--ok)}
.qfeed .res.no{color:var(--red)}
.qfoot{display:flex;gap:9px;align-items:center;margin-top:18px}
.score{margin-left:auto;font-size:12.5px;color:var(--muted);font-family:var(--mono)}
.btn{
  padding:7px 15px;border-radius:9px;border:1px solid var(--line);background:var(--card);
  font-size:13px;color:var(--ink-2);transition:.15s;
}
.btn:hover{border-color:#c9d3cf;box-shadow:var(--shadow)}
.btn.primary{background:var(--accent);border-color:var(--accent);color:#fff}
.btn.primary:hover{background:#12564c}

/* flashcards */
.fc-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:12px}
.fcard-flip{perspective:1000px;height:172px;cursor:pointer}
.fcard-inner{position:relative;width:100%;height:100%;transition:transform .5s cubic-bezier(.2,.8,.3,1);transform-style:preserve-3d}
.fcard-flip.flipped .fcard-inner{transform:rotateY(180deg)}
.fc-face{
  position:absolute;inset:0;backface-visibility:hidden;border-radius:12px;
  padding:14px 16px;display:flex;flex-direction:column;gap:7px;
  background:var(--card);border:1px solid var(--line);box-shadow:var(--shadow);overflow:hidden;
}
.fc-face.front{justify-content:center;align-items:center;text-align:center;background:linear-gradient(160deg,#fffefb,#f7f6f0)}
.fc-face.front b{font-size:15px}
.fc-face.front span{font-size:11px;color:var(--muted);letter-spacing:.06em}
.fc-face.back{transform:rotateY(180deg);font-size:12.5px;line-height:1.65;color:var(--ink-2);overflow:auto}
.fc-face.back .ttl{font-size:11px;letter-spacing:.1em;color:var(--accent);font-weight:700;text-transform:uppercase}

/* ---------- sprint ---------- */
.sprint-head{
  display:flex;align-items:center;gap:18px;flex-wrap:wrap;
  background:linear-gradient(135deg,#1b1f22,#2b3136);color:#f0f3f2;
  border-radius:18px;padding:22px 26px;margin-bottom:22px;box-shadow:var(--shadow-lg);
}
.sprint-head h1{margin:0;font-size:21px;letter-spacing:.02em}
.sprint-head p{margin:4px 0 0;font-size:12.5px;color:rgba(240,243,242,.6)}
.timer{font-family:var(--mono);font-size:30px;letter-spacing:.03em;margin-left:auto}
.timer.warn{color:#f2b544}
.sprint-cols{display:grid;grid-template-columns:1.15fr .85fr;gap:18px;align-items:start}
.done-bar{height:6px;border-radius:99px;background:var(--paper-2);overflow:hidden;margin:0 0 16px}
.done-bar i{display:block;height:100%;background:linear-gradient(90deg,#2b8a76,#17594f);transition:width .35s}
.check-item{
  display:flex;gap:11px;align-items:flex-start;padding:11px 14px;border-radius:10px;
  background:var(--card);border:1px solid var(--line);margin-bottom:8px;cursor:pointer;transition:.15s;
}
.check-item:hover{border-color:#cfd8d4}
.check-item .box{
  flex:0 0 17px;height:17px;border-radius:5px;border:1.5px solid #cfd5d1;margin-top:2px;
  display:grid;place-items:center;color:transparent;font-size:11px;transition:.15s;
}
.check-item.done{opacity:.55}
.check-item.done .box{background:var(--accent);border-color:var(--accent);color:#fff}
.check-item.done .t{text-decoration:line-through;text-decoration-color:#9fb5ad}
.check-item .t{font-size:13.3px;line-height:1.65}
.check-item .d{font-size:11.5px;color:var(--muted);margin-top:2px;line-height:1.55}
.sprint-sec{margin:0 0 24px}
.sprint-sec h2{font-size:12px;letter-spacing:.14em;text-transform:uppercase;color:var(--muted);margin:0 0 10px;display:flex;align-items:center;gap:9px}
.sprint-sec h2::after{content:"";flex:1;height:1px;background:var(--line)}

/* ---------- modal / lightbox ---------- */
.modal{position:fixed;inset:0;z-index:100;background:rgba(20,24,26,.42);backdrop-filter:blur(3px);display:flex;align-items:flex-start;justify-content:center;padding:9vh 16px 16px}
.modal.hidden{display:none}
.modal-box.wide{max-width:860px}
.sheet-h{font-size:12px;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);margin:18px 0 8px;font-weight:600}
.sheet-h:first-child{margin-top:2px}
.sheet-p{font-size:13.6px;line-height:1.85;color:var(--ink-2);margin:0 0 12px;padding:0 18px}
.sheet-body-inner{padding:14px 0 20px}
.idx-list{display:grid;grid-template-columns:1fr 1fr;gap:6px 18px;padding:0 18px}
.idx-list a{font-size:13px;color:var(--ink-2);padding:4px 0;border-bottom:1px dashed var(--line-2);display:flex;gap:8px}
.idx-list a b{color:var(--accent);font-family:var(--mono);font-size:11px;font-weight:600;padding-top:2px}
.idx-list a:hover{color:var(--accent)}
.modal-box{width:100%;max-width:760px;background:var(--card);border-radius:16px;box-shadow:var(--shadow-lg);overflow:hidden;display:flex;flex-direction:column;max-height:78vh}
.modal-head{display:flex;align-items:center;gap:10px;padding:13px 16px;border-bottom:1px solid var(--line);color:var(--muted)}
.modal-head input{flex:1;border:0;outline:0;font-size:15px;background:transparent;color:var(--ink)}
.modal-close{border:1px solid var(--line);background:var(--paper-2);border-radius:6px;font-size:10.5px;padding:3px 7px;color:var(--muted);font-family:var(--mono)}
.modal-body{overflow:auto;padding:6px 0}
.sr{display:flex;gap:11px;padding:10px 16px;border-bottom:1px solid var(--line-2);align-items:flex-start}
.sr:hover{background:#faf9f4}
.sr .k{flex:0 0 auto;font-size:10px;padding:2px 6px;border-radius:4px;background:var(--paper-2);border:1px solid var(--line);color:var(--muted);margin-top:2px}
.sr .t{font-size:13px;line-height:1.6}
.sr .t em{font-style:normal;color:var(--muted);font-size:11.5px;display:block;margin-top:2px}
.sr mark{background:#fbeecb;color:inherit;border-radius:2px}
.empty{padding:26px 16px;text-align:center;color:var(--muted);font-size:13px}

.lightbox{position:fixed;inset:0;z-index:200;background:rgba(10,12,13,.94);display:flex;align-items:center;justify-content:center}
.lightbox.hidden{display:none}
.lightbox img{max-width:96vw;max-height:92vh;object-fit:contain;border-radius:6px}
.lb-close{position:absolute;top:18px;right:22px;background:rgba(255,255,255,.1);border:0;color:#fff;width:34px;height:34px;border-radius:9px;font-size:15px}
.lb-nav{position:absolute;top:50%;transform:translateY(-50%);background:rgba(255,255,255,.09);border:0;color:#fff;width:46px;height:72px;font-size:30px;border-radius:10px}
.lb-nav:hover{background:rgba(255,255,255,.18)}
.lb-prev{left:18px}.lb-next{right:18px}

.hidden{display:none!important}

/* ---------- responsive ---------- */
@media(max-width:1180px){
  .reader-body{grid-template-columns:minmax(0,1fr)}
  .panel{position:static;max-height:none}
  .sprint-cols{grid-template-columns:1fr}
}
@media(max-width:820px){
  .topbar{height:auto;flex-wrap:wrap;padding:8px 14px;gap:8px}
  .nav{order:3;width:100%;flex-wrap:wrap;row-gap:2px;padding-bottom:2px}
  .nav a{white-space:nowrap}
  .search-btn span,.search-btn kbd{display:none}
  main{padding:18px 14px 70px}
  .hero{padding:24px 22px}
  .hero h1{font-size:24px}
  .course-strip{grid-template-columns:1fr}
  .gap-card ul{columns:1}
  .ch-grid{grid-template-columns:1fr}
  .panel{position:static}
}

/* ---------- 手机 / 触屏 ---------- */
.mtabs{display:none}
@media (hover:none),(pointer:coarse){
  .stage-nav{opacity:1;width:44px;height:66px;font-size:26px}
  .stage-nav.prev{border-radius:0 10px 10px 0}
  .stage-nav.next{border-radius:10px 0 0 10px}
  .thumb img{width:104px;height:58px}
}
@media(max-width:900px){
  .mtabs{display:flex;gap:4px;margin:0 0 10px;background:var(--card);border:1px solid var(--line);border-radius:11px;padding:3px;box-shadow:var(--shadow)}
  .mtabs button{flex:1;border:0;background:transparent;padding:9px 4px;border-radius:8px;font-size:13.5px;color:var(--muted)}
  .mtabs button.on{background:var(--accent);color:#fff;font-weight:600}
  .reader[data-mtab="slide"] .panel{display:none}
  .reader[data-mtab="text"] .stage-wrap,
  .reader[data-mtab="text"] .thumbs{display:none}
  .reader[data-mtab="text"] .panel{max-height:none}
  .reader-top [data-act="zoom"]{display:none}
  .stage-wrap img{max-height:none;width:100%}
  .panel{max-height:none;position:static}
  .panel-body h4{font-size:18px}
  .gist{font-size:13.6px}
  .bullet .zh{font-size:13.6px}
  .bullet .en{font-size:12.2px}
  .st-btn{padding:9px 4px;font-size:12px}
  .nav a{padding:7px 10px}
}

/* ---------- print ---------- */
@media print{
  body{background:#fff;font-size:11pt}
  .topbar,.thumbs,.panel,.status-bar,.modal,.lightbox,.toolbar,.sprint-head,.search-btn{display:none!important}
  main{padding:0;max-width:none}
  .fgrid{grid-template-columns:1fr 1fr;gap:6px}
  .fcard{box-shadow:none;break-inside:avoid;border-color:#ccc}
  .fgroup{break-inside:avoid}
  .view-head h1{font-size:16pt}
  a[href]:after{content:""}
}