:root{
  --bg:#fff; --bg-2:#fafafa; --bg-3:#f4f4f4;
  --ink:#0a0a0a; --mute:#5b5b5b; --line:#ececec;
  --y:#FFD60A; --y-d:#f5c400; --y-l:#fff7c2;
  --shadow-sm:0 4px 16px rgba(0,0,0,.04);
  --shadow:0 12px 40px rgba(0,0,0,.07);
  --r:16px; --ease:cubic-bezier(.22,1,.36,1);
  --read:"Noto Serif TC","Source Serif Pro",Georgia,serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;scroll-padding-top:90px}
body{font-family:"Inter","Noto Sans TC",system-ui,sans-serif;
  color:var(--ink);background:var(--bg);line-height:1.7;-webkit-font-smoothing:antialiased;overflow-x:hidden}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
button{font-family:inherit;cursor:pointer;border:none;background:none}
.container{max-width:1280px;margin:0 auto;padding:0 24px}

/* ===== NAV ===== */
.nav{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.85);
  backdrop-filter:saturate(180%) blur(16px);-webkit-backdrop-filter:saturate(180%) blur(16px);
  border-bottom:1px solid var(--line)}
.nav-inner{display:flex;align-items:center;justify-content:space-between;height:74px}
.brand{font-weight:800;letter-spacing:-.02em;font-size:1.3rem;display:flex;align-items:center;gap:6px}
.brand .dot{display:inline-block;width:10px;height:10px;background:var(--y);border-radius:50%;
  box-shadow:0 0 0 4px var(--y-l);animation:pulse 2.4s var(--ease) infinite}
@keyframes pulse{50%{box-shadow:0 0 0 8px rgba(255,214,10,.15)}}
.menu{display:flex;gap:12px;list-style:none;white-space:nowrap}
.menu a{position:relative;font-weight:500;font-size:.78rem;padding:6px 0;color:#222;transition:color .3s}
.nav-inner nav{overflow-x:auto;max-width:calc(100% - 300px);-webkit-overflow-scrolling:touch;scrollbar-width:none}
.nav-inner nav::-webkit-scrollbar{display:none}
.menu a::after{content:"";position:absolute;left:0;bottom:-2px;width:0;height:2px;background:var(--y-d);transition:width .4s var(--ease)}
.menu a:hover::after,.menu a.active::after{width:100%}
.menu a.active{color:#000;font-weight:700}
.nav-cta{display:flex;align-items:center;gap:14px}

.burger{display:none;width:46px;height:46px;border:1px solid var(--line);border-radius:14px;background:#fff;position:relative;
  transition:transform .45s var(--ease),background .3s,border-color .3s}
.burger:hover{background:var(--y);border-color:var(--y-d);transform:rotate(90deg)}
.burger span{position:absolute;left:50%;top:50%;width:20px;height:2px;background:var(--ink);border-radius:2px;transition:transform .5s var(--ease),opacity .3s}
.burger span:nth-child(1){transform:translate(-50%,-7px)}
.burger span:nth-child(2){transform:translate(-50%,-50%)}
.burger span:nth-child(3){transform:translate(-50%,5px)}
.burger.open{transform:rotate(180deg);background:var(--y)}
.burger.open span:nth-child(1){transform:translate(-50%,-50%) rotate(45deg)}
.burger.open span:nth-child(2){opacity:0;transform:translate(-50%,-50%) scale(.2)}
.burger.open span:nth-child(3){transform:translate(-50%,-50%) rotate(-45deg)}

.drawer{position:fixed;inset:74px 0 0 0;background:#fff;transform:translateY(-110%);
  transition:transform .6s var(--ease);z-index:40;padding:32px 24px;overflow-y:auto}
.drawer.open{transform:translateY(0)}
.drawer ul{list-style:none;display:flex;flex-direction:column;gap:6px}
.drawer a{display:flex;justify-content:space-between;align-items:center;padding:18px 20px;border-radius:14px;font-size:1.2rem;font-weight:600;border:1px solid transparent;transition:all .35s var(--ease)}
.drawer a::after{content:"→";opacity:0;transition:opacity .3s,transform .3s}
.drawer a:hover{background:var(--y);border-color:var(--y-d);transform:translateX(8px)}
.drawer a:hover::after{opacity:1;transform:translateX(4px)}

/* === Reading progress bar === */
.progress{position:fixed;top:73px;left:0;height:3px;width:0%;background:var(--y-d);z-index:51;
  transition:width .15s linear;box-shadow:0 0 8px rgba(245,196,0,.6)}

/* === Buttons === */
.btn{display:inline-flex;align-items:center;gap:10px;padding:13px 24px;border-radius:999px;font-weight:600;font-size:.95rem;border:1px solid var(--ink);
  transition:transform .35s var(--ease),background .3s,color .3s,box-shadow .3s}
.btn:hover{transform:translateY(-3px)}
.btn-primary{background:var(--y);border-color:var(--y);color:#000}
.btn-primary:hover{background:var(--y-d);box-shadow:0 12px 30px rgba(245,196,0,.35)}
.btn-ghost{background:transparent}
.btn-ghost:hover{background:var(--ink);color:#fff}
.btn .arr{display:inline-block;transition:transform .3s var(--ease)}
.btn:hover .arr{transform:translateX(4px)}

/* === Common === */
.eyebrow{display:inline-block;font-size:.78rem;font-weight:700;letter-spacing:.18em;text-transform:uppercase;background:var(--y);padding:7px 14px;border-radius:6px;color:#000}

/* ===== Article Hero ===== */
.art-hero{padding:80px 0 50px;border-bottom:1px solid var(--line);position:relative;overflow:hidden}
.art-hero .blob{position:absolute;width:480px;height:480px;border-radius:50%;
  background:radial-gradient(circle,var(--y-l) 0%,transparent 70%);
  filter:blur(50px);z-index:-1;right:-120px;top:-160px;animation:blob 16s var(--ease) infinite}
@keyframes blob{50%{transform:translate(-30px,40px) scale(1.1)}}
.crumbs{display:flex;gap:8px;font-size:.85rem;color:var(--mute);margin-bottom:24px}
.crumbs a:hover{color:#000}
.crumbs span{color:#bbb}
.art-hero h1{font-size:clamp(2.4rem,6vw,4.6rem);font-weight:800;letter-spacing:-.035em;line-height:1.05;max-width:920px}
.art-hero h1 mark{background:var(--y);padding:0 .12em;border-radius:8px}
.art-hero .lede{margin-top:24px;font-size:1.15rem;color:var(--mute);max-width:760px;font-family:var(--read)}
.art-hero .meta{margin-top:36px;display:flex;flex-wrap:wrap;gap:28px;align-items:center}
.art-hero .meta .who{display:flex;align-items:center;gap:12px}
.art-hero .meta .av{width:42px;height:42px;border-radius:50%;background:var(--y);display:grid;place-items:center;font-weight:800}
.art-hero .meta b{display:block;font-size:.92rem}
.art-hero .meta span{display:block;font-size:.82rem;color:var(--mute)}
.art-hero .meta .pill{padding:8px 14px;background:var(--bg-2);border:1px solid var(--line);border-radius:99px;font-size:.82rem;font-weight:600}

/* ===== Layout ===== */
.layout{display:grid;grid-template-columns:240px minmax(0,1fr) 240px;gap:60px;padding:60px 0 80px}
.toc{position:sticky;top:100px;align-self:start;max-height:calc(100vh - 120px);overflow-y:auto;
  padding-right:8px}
.toc h5{font-size:.72rem;font-weight:800;letter-spacing:.2em;text-transform:uppercase;color:var(--mute);margin-bottom:14px}
.toc ol{list-style:none;display:flex;flex-direction:column;gap:2px;border-left:1px solid var(--line);padding-left:0}
.toc a{display:block;padding:8px 14px;font-size:.88rem;color:var(--mute);border-left:2px solid transparent;
  margin-left:-1px;transition:all .3s}
.toc a:hover{color:#000;background:var(--bg-2)}
.toc a.active{color:#000;border-left-color:var(--y-d);font-weight:600;background:linear-gradient(to right,var(--y-l),transparent)}

/* === Article body === */
article{max-width:760px;font-family:var(--read);font-size:1.08rem;line-height:1.85}
article > section{margin-bottom:64px;scroll-margin-top:90px}
article h2{font-family:"Inter","Noto Sans TC",sans-serif;font-size:clamp(1.6rem,3vw,2.2rem);
  font-weight:800;letter-spacing:-.025em;line-height:1.2;margin:8px 0 22px;
  display:flex;align-items:baseline;gap:14px}
article h2 .num{font-family:"Playfair Display",serif;font-style:italic;color:var(--y-d);font-size:.85em;font-weight:700}
article h3{font-family:"Inter","Noto Sans TC",sans-serif;font-size:1.25rem;font-weight:700;letter-spacing:-.01em;margin:32px 0 14px}
article p{margin-bottom:20px;color:#1a1a1a}
article p.first::first-letter{font-family:"Playfair Display",serif;font-weight:700;font-style:italic;
  font-size:4.4rem;float:left;line-height:.9;padding:6px 12px 0 0;color:var(--y-d)}
article a{border-bottom:1px solid var(--y);transition:background .3s}
article a:hover{background:var(--y-l)}
article strong{font-weight:700;background:linear-gradient(transparent 60%,var(--y-l) 60%);padding:0 2px}
article em{font-style:italic;font-family:"Playfair Display",serif}
article ul,article ol{margin:0 0 24px 24px;color:#1a1a1a}
article li{margin-bottom:8px}
article blockquote{margin:30px 0;padding:24px 30px;border-left:4px solid var(--y);background:var(--bg-2);border-radius:0 12px 12px 0;font-style:italic;font-size:1.1rem;color:#222}
article blockquote::before{content:"\201C";font-family:"Playfair Display",serif;font-size:3rem;line-height:0;color:var(--y-d);vertical-align:-.4em;margin-right:6px}

/* Callouts */
.callout{margin:30px 0;padding:24px 28px;border-radius:14px;border:1px solid var(--line);
  background:var(--bg-2);position:relative;font-family:"Inter","Noto Sans TC",sans-serif;font-size:.97rem}
.callout.tip{background:var(--y-l);border-color:var(--y)}
.callout.warn{background:#fff;border-left:4px solid #000}
.callout.def{background:#fff;border:2px solid var(--ink);border-radius:14px}
.callout h4{font-size:.78rem;letter-spacing:.18em;text-transform:uppercase;font-weight:800;margin-bottom:8px}
.callout.tip h4{color:#664a00}
.callout.warn h4{color:#000}
.callout p{margin:0;color:#222}

/* Formula */
.formula{margin:28px 0;padding:30px;background:#0a0a0a;color:#fff;border-radius:16px;
  text-align:center;font-family:"JetBrains Mono",monospace;font-size:1.4rem;letter-spacing:.02em;
  position:relative;overflow:hidden}
.formula::before{content:"FORMULA";position:absolute;top:14px;left:18px;font-size:.7rem;letter-spacing:.2em;color:var(--y);font-family:"Inter",sans-serif;font-weight:700}
.formula em{color:var(--y);font-style:normal}

/* Table */
.tbl{margin:28px 0;border:1px solid var(--line);border-radius:14px;overflow:hidden}
table{width:100%;border-collapse:collapse;font-family:"Inter","Noto Sans TC",sans-serif;font-size:.94rem}
th{background:var(--bg-2);text-align:left;padding:14px 18px;font-weight:700;border-bottom:1px solid var(--line)}
td{padding:14px 18px;border-bottom:1px solid var(--line)}
tr:last-child td{border-bottom:none}
tr:hover td{background:var(--y-l)}

/* Inline chart (compounding bars) */
.chart{margin:30px 0;padding:24px;background:#fff;border:1px solid var(--line);border-radius:16px;font-family:"Inter",sans-serif}
.chart h4{font-size:.85rem;letter-spacing:.1em;text-transform:uppercase;font-weight:700;color:var(--mute);margin-bottom:18px}
.bars{display:flex;flex-direction:column;gap:14px}
.bar-row{display:grid;grid-template-columns:60px 1fr 80px;gap:14px;align-items:center}
.bar-row .lbl{font-weight:600;font-size:.9rem;color:#222}
.bar-row .track{height:18px;background:var(--bg-3);border-radius:99px;overflow:hidden;position:relative}
.bar-row .fill{height:100%;background:linear-gradient(90deg,var(--y),var(--y-d));border-radius:99px;width:0;transition:width 1.4s var(--ease)}
.bar-row.in .fill{width:var(--w)}
.bar-row .val{font-weight:700;font-size:.95rem;text-align:right}

/* Right rail (key takeaways) */
.rail{position:sticky;top:100px;align-self:start;display:flex;flex-direction:column;gap:18px}
.rail .box{background:var(--bg-2);border:1px solid var(--line);border-radius:16px;padding:20px}
.rail .box h5{font-size:.72rem;letter-spacing:.18em;text-transform:uppercase;font-weight:800;margin-bottom:12px}
.rail .box ul{list-style:none;display:flex;flex-direction:column;gap:10px}
.rail .box li{font-size:.88rem;color:#222;padding-left:16px;position:relative}
.rail .box li::before{content:"";position:absolute;left:0;top:9px;width:6px;height:6px;border-radius:50%;background:var(--y-d)}
.rail .share{display:flex;flex-direction:column;gap:8px}
.rail .share button{padding:10px 14px;border:1px solid var(--line);border-radius:10px;background:#fff;font-size:.85rem;font-weight:600;text-align:left;transition:all .3s}
.rail .share button:hover{background:var(--y);border-color:var(--y-d);transform:translateX(4px)}

/* Reveal */
.reveal{opacity:0;transform:translateY(40px);transition:opacity .9s var(--ease),transform .9s var(--ease)}
.reveal.in{opacity:1;transform:none}
.reveal-d2{transition-delay:.12s}
.reveal-d3{transition-delay:.24s}

/* ===== Quiz ===== */
.quiz{margin:60px 0;padding:40px;background:var(--ink);color:#fff;border-radius:20px}
.quiz h3{color:#fff;font-size:1.4rem;margin-bottom:8px;font-family:"Inter",sans-serif}
.quiz p.q{color:#bbb;margin-bottom:20px;font-family:"Inter",sans-serif}
.quiz .opts{display:flex;flex-direction:column;gap:10px}
.quiz .opt{padding:14px 18px;background:#1a1a1a;border:1px solid #2a2a2a;border-radius:12px;cursor:pointer;
  font-family:"Inter",sans-serif;font-size:.95rem;text-align:left;color:#eee;transition:all .3s var(--ease)}
.quiz .opt:hover{background:#222;border-color:var(--y);transform:translateX(4px)}
.quiz .opt.correct{background:var(--y);color:#000;border-color:var(--y);font-weight:700}
.quiz .opt.wrong{background:#3a1010;border-color:#a00;color:#fff}
.quiz .feedback{margin-top:18px;font-size:.9rem;color:var(--y);min-height:24px;font-family:"Inter",sans-serif}

/* Chapter nav */
.chap-nav{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-top:60px}
.chap-nav a{padding:24px 28px;border:1px solid var(--line);border-radius:16px;display:block;
  transition:all .4s var(--ease);background:#fff;font-family:"Inter",sans-serif}
.chap-nav a:hover{background:var(--y-l);border-color:var(--y);transform:translateY(-4px)}
.chap-nav .lbl{font-size:.72rem;letter-spacing:.18em;text-transform:uppercase;color:var(--mute);font-weight:700}
.chap-nav .ttl{margin-top:8px;font-weight:700;font-size:1.05rem}
.chap-nav .next{text-align:right}

/* CTA */
.cta-band{background:var(--y);border-radius:24px;padding:54px 44px;display:grid;grid-template-columns:1.4fr 1fr;gap:40px;align-items:center;margin-top:60px}
.cta-band h2{margin:0;font-family:"Inter",sans-serif;font-size:clamp(1.6rem,3vw,2.2rem);font-weight:800;letter-spacing:-.02em}
.cta-band a.btn{background:#000;color:var(--y);border-color:#000}

/* Footer */
footer{background:var(--ink);color:#eaeaea;padding:72px 0 28px;margin-top:80px}
.f-grid{display:grid;grid-template-columns:1.5fr 1fr 1fr 1fr;gap:40px}
footer h5{font-size:.85rem;letter-spacing:.12em;text-transform:uppercase;color:#fff;margin-bottom:18px}
footer ul{list-style:none;display:flex;flex-direction:column;gap:10px}
footer a{color:#bdbdbd;font-size:.92rem;transition:color .3s}
footer a:hover{color:var(--y)}
.f-bottom{margin-top:48px;padding-top:24px;border-top:1px solid #222;display:flex;justify-content:space-between;color:#999;font-size:.85rem;flex-wrap:wrap;gap:12px}

/* ===== Responsive ===== */
@media(max-width:1100px){
  .layout{grid-template-columns:200px minmax(0,1fr);gap:40px}
  .rail{display:none}
}
@media(max-width:860px){
  .menu,.nav-cta .btn{display:none}
  .burger{display:block}
  .layout{grid-template-columns:1fr;gap:30px;padding:40px 0 60px}
  .toc{position:relative;top:0;max-height:none;border:1px solid var(--line);border-radius:14px;padding:18px;background:var(--bg-2)}
  .toc ol{border-left:none}
  .chap-nav{grid-template-columns:1fr}
  .cta-band{grid-template-columns:1fr;padding:40px 28px}
  .f-grid{grid-template-columns:repeat(2,1fr)}
}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}