@import url('https://fonts.googleapis.com/css2?family=Lexend:wght@300;400;500;600;700&family=Source+Sans+3:wght@300;400;500;600;700&display=swap');

:root{
  --navy:#0F1B2B;
  --orange:#FF6B35;
  --paper:#F7F7F5;
  --ink:#1B2A3D;
  --line:#DEE0DC;
  --muted:#5B6472;
  --max:1180px;
}

*,*::before,*::after{box-sizing:border-box}

html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}

body{
  margin:0;
  background:var(--paper);
  color:var(--navy);
  font-family:'Lexend','Source Sans 3',system-ui,-apple-system,'Segoe UI',Roboto,'PingFang SC','Hiragino Sans GB','Microsoft YaHei',sans-serif;
  font-size:17px;
  line-height:1.75;
  -webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}

img{max-width:100%;height:auto;display:block}
a{color:inherit;text-decoration:none}
h1,h2,h3,h4{line-height:1.25;margin:0;letter-spacing:-0.01em}
::selection{background:var(--orange);color:var(--navy)}

.sr-only{
  position:absolute;width:1px;height:1px;padding:0;margin:-1px;
  overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0;
}

/* 顶栏 */
.top{
  position:sticky;top:0;z-index:60;
  display:flex;align-items:center;justify-content:space-between;gap:10px;
  padding:8px 18px;
  background:var(--navy);
  color:var(--paper);
  border-bottom:3px solid var(--orange);
}

.nav-side{min-width:0}
.nav-side ul{display:flex;flex-wrap:wrap;list-style:none;margin:0;padding:0;gap:2px}
.nav-side a{
  display:inline-flex;align-items:center;gap:7px;
  min-height:44px;padding:6px 10px;
  font-size:15px;font-weight:500;line-height:1.2;
  color:var(--paper);border-radius:4px;
  transition:background-color .18s ease,color .18s ease;
}
.nav-side a svg{
  width:16px;height:16px;flex:none;
  fill:none;stroke:currentColor;stroke-width:1.8;
  stroke-linecap:round;stroke-linejoin:round;
}
.nav-side a:hover,.nav-side a:focus-visible{background:var(--orange);color:var(--navy);outline:none}

.brand{
  display:inline-flex;align-items:center;gap:9px;
  min-height:44px;padding:6px 14px;
  border:2px solid var(--orange);border-radius:4px;
  font-size:16px;font-weight:700;letter-spacing:.02em;
  color:var(--paper);white-space:nowrap;
  transition:background-color .18s ease,color .18s ease;
}
.brand b{font-weight:700}
.brand-mark{display:inline-flex}
.brand-mark svg{
  width:20px;height:20px;
  fill:none;stroke:currentColor;stroke-width:2;
  stroke-linecap:round;stroke-linejoin:round;
}
.brand:hover,.brand:focus-visible{background:var(--orange);color:var(--navy);outline:none}

/* 头部主视觉 */
.hero{
  background-color:var(--navy);
  background-image:radial-gradient(rgba(255,107,53,.5) 1.3px,transparent 1.3px);
  background-size:20px 20px;
  padding:36px 20px;
  display:flex;justify-content:center;align-items:center;
  min-height:45vh;
}
.hero-in{
  display:flex;align-items:center;gap:24px;
  max-width:840px;
  padding:26px 30px;
  background:var(--navy);
  border:2px solid var(--orange);
  border-radius:4px;
  color:var(--paper);
}
.hero-mark{display:inline-flex;flex:none}
.hero-mark svg{
  width:62px;height:62px;
  fill:none;stroke:var(--orange);stroke-width:2.6;
  stroke-linecap:round;stroke-linejoin:round;
}
.hero-txt{min-width:0}
.hero h1{
  font-size:clamp(25px,4.2vw,40px);
  font-weight:700;
  letter-spacing:-.02em;
}
.lede{
  margin:12px 0 0;
  max-width:46ch;
  font-size:16px;
  font-weight:300;
  line-height:1.7;
  color:rgba(247,247,245,.8);
}

/* 版心：左栏 + 正文 */
.wrap{
  max-width:var(--max);
  margin:0 auto;
  padding:34px 20px 8px;
  display:grid;
  grid-template-columns:238px minmax(0,1fr);
  gap:34px;
  align-items:start;
}

.side{
  position:sticky;top:78px;
  background:#fff;
  border:2px solid var(--navy);
  border-bottom:5px solid var(--orange);
  border-radius:10px;
  padding:16px 16px 18px;
}
.side-h{
  display:flex;align-items:center;
  font-size:14px;font-weight:700;
  letter-spacing:.18em;
  color:var(--muted);
}
.side-nav ul{list-style:none;margin:10px 0 0;padding:0}
.side-nav a{
  display:flex;align-items:center;
  min-height:40px;
  padding:4px 0 4px 12px;
  border-left:2px solid var(--line);
  font-size:15px;line-height:1.35;
  transition:border-color .18s ease,color .18s ease;
}
.side-nav a:hover,.side-nav a:focus-visible{border-color:var(--orange);color:var(--orange);outline:none}

.top-link{
  display:flex;align-items:center;justify-content:center;
  min-height:40px;margin-top:14px;
  border:2px solid var(--navy);border-radius:4px;
  font-size:14px;font-weight:600;
  transition:background-color .18s ease,color .18s ease;
}
.top-link:hover,.top-link:focus-visible{background:var(--navy);color:var(--paper);outline:none}

/* 正文 */
.body-sec{min-width:0}
.prose{max-width:770px;overflow-wrap:anywhere}

.prose section{
  background:#fff;
  border:2px solid var(--line);
  border-bottom:4px solid var(--orange);
  border-radius:10px;
  padding:24px 24px 10px;
  margin:0 0 22px;
  scroll-margin-top:96px;
}
.prose section:last-child{margin-bottom:0}

.prose h2{
  display:flex;align-items:baseline;gap:10px;
  margin:4px 0 14px;
  padding-left:14px;
  border-left:6px solid var(--orange);
  font-size:clamp(20px,2.3vw,25px);
  font-weight:700;
}
.prose h3{
  display:flex;align-items:baseline;gap:9px;
  margin:22px 0 10px;
  padding-left:11px;
  border-left:3px solid var(--navy);
  font-size:18px;
  font-weight:600;
}
.prose h2 span,.prose h3 span{min-width:0}

.prose p{margin:0 0 16px;color:var(--ink)}
.prose ul,.prose ol{margin:0 0 16px;padding-left:24px}
.prose li{margin:0 0 8px;color:var(--ink)}
.prose li::marker{color:var(--orange);font-weight:700}

.prose a{color:var(--orange);border-bottom:2px solid rgba(255,107,53,.35);font-weight:500}
.prose a:hover{border-bottom-color:var(--orange)}

.prose strong{font-weight:700;color:var(--navy)}
.prose blockquote{
  margin:0 0 16px;
  padding:12px 18px;
  border-left:6px solid var(--navy);
  background:var(--paper);
  border-radius:4px;
  color:var(--muted);
}
.prose blockquote p:last-child{margin-bottom:0}
.prose code{
  font-size:15px;
  background:var(--paper);
  border:1px solid var(--line);
  border-radius:3px;
  padding:1px 5px;
}
.prose pre{
  margin:0 0 16px;padding:14px;
  background:var(--navy);color:var(--paper);
  border-radius:4px;overflow-x:auto;
}
.prose pre code{background:none;border:0;color:inherit;padding:0}
.prose table{width:100%;border-collapse:collapse;margin:0 0 16px;font-size:15px}
.prose th,.prose td{border:1px solid var(--line);padding:8px 10px;text-align:left}
.prose th{background:var(--paper);font-weight:600}
.prose img{border-radius:4px;margin:0 0 16px}

/* 订阅块 */
.cta{max-width:var(--max);margin:14px auto 0;padding:0 20px}
.cta-in{
  display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:16px;
  padding:22px 24px;
  background:#fff;
  border:2px solid var(--navy);
  border-bottom:5px solid var(--orange);
  border-radius:10px;
}
.cta-h{
  display:flex;align-items:center;
  font-size:19px;font-weight:700;
}
.sub{display:flex;flex-wrap:wrap;gap:10px}
.sub input{
  min-height:44px;width:230px;max-width:100%;
  padding:0 12px;
  font:inherit;font-size:16px;
  color:var(--navy);
  background:var(--paper);
  border:2px solid var(--navy);
  border-radius:4px;
}
.sub input:focus-visible{outline:3px solid var(--orange);outline-offset:1px}
.sub button{
  min-height:44px;padding:0 24px;
  font:inherit;font-size:16px;font-weight:700;
  color:var(--navy);background:var(--orange);
  border:2px solid var(--navy);border-radius:4px;
  cursor:pointer;
  transition:background-color .18s ease,color .18s ease;
}
.sub button:hover,.sub button:focus-visible{background:var(--navy);color:var(--paper);outline:none}

/* 页脚 */
.foot{
  margin-top:34px;
  padding:26px 20px;
  background:var(--navy);
  border-top:4px solid var(--orange);
  color:rgba(247,247,245,.7);
  text-align:center;
}
.foot p{margin:0 0 6px;color:var(--paper);font-size:15px;font-weight:600}
.foot small{font-size:13px;line-height:1.6}

/* 入场动效 */
.js .prose section{opacity:0;transform:translateY(10px);transition:opacity .3s ease,transform .3s ease}
.js .prose section.in{opacity:1;transform:none}

@media (max-width:900px){
  .wrap{grid-template-columns:minmax(0,1fr);gap:22px;padding-top:24px}
  .side{position:static;order:2}
  .side-nav ul{display:grid;grid-template-columns:1fr 1fr;gap:0 14px}
}

@media (max-width:860px){
  .top{flex-wrap:wrap;padding:8px 12px;gap:6px}
  .brand{order:-1;width:100%;justify-content:center;font-size:15px;margin-bottom:2px}
  .nav-side{flex:1 1 100%}
  .nav-side ul{justify-content:center}
  .nav-side a{font-size:14px;padding:6px 9px;gap:5px}
  .hero{padding:28px 14px}
  .hero-in{flex-direction:column;text-align:center;gap:16px;padding:24px 20px}
  .hero-mark svg{width:48px;height:48px}
  .lede{max-width:none}
  .prose section{padding:20px 18px 8px;scroll-margin-top:120px}
  .cta-in{padding:18px}
  .sub input{flex:1 1 180px;width:auto}
}

@media (max-width:560px){
  .nav-side a svg{display:none}
  .nav-side a{padding:6px 8px}
  .side-nav ul{grid-template-columns:1fr}
  .cta-h{font-size:17px}
}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *{transition:none !important;animation:none !important}
  .js .prose section{opacity:1;transform:none}
}

button[aria-expanded]{min-width:44px;min-height:44px}