:root{
  --bg: #fafafa;
  --bg-alt: #ffffff;
  --ink: #1d1d1f;
  --ink-2: #424245;
  --muted: #86868b;
  --line: #e8e8ed;
  --blue: #0071e3;
  --blue-soft: #e8f1ff;
  --radius: 14px;
  --font-zh: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", sans-serif;
  --font-en: "SF Pro Display", -apple-system, BlinkMacSystemFont, "Inter", "Helvetica Neue", Arial, sans-serif;
}

*{margin:0;padding:0;box-sizing:border-box;}
html{scroll-behavior:smooth;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;}
body{
  font-family:var(--font-zh);
  background:var(--bg);
  color:var(--ink);
  line-height:1.7;
  font-weight:400;
  letter-spacing:.01em;
}
html[lang="en"] body{ font-family:var(--font-en); letter-spacing:-.003em; }
a{color:var(--blue);text-decoration:none;transition:opacity .2s;}
a:hover{opacity:.7;}
img{display:block;}

/* NAV */
.nav{
  position:sticky; top:0;
  display:flex; align-items:center; justify-content:space-between;
  height:52px;
  padding:0 28px;
  background:rgba(250,250,250,.82);
  backdrop-filter:saturate(180%) blur(20px);
  -webkit-backdrop-filter:saturate(180%) blur(20px);
  border-bottom:1px solid rgba(0,0,0,.06);
  z-index:100;
  font-size:13px;
}
.nav-brand{display:flex;align-items:center;gap:10px;font-weight:500;color:var(--ink);}
.nav-brand img{width:22px;height:22px;border-radius:6px;}
.nav-brand .en{color:var(--muted); font-family:var(--font-en); font-size:12px; letter-spacing:.02em;}
.nav-langs{
  display:flex; align-items:center; gap:0;
  border:1px solid var(--line);
  border-radius:999px;
  background:rgba(255,255,255,.6);
  padding:2px;
}
.nav-langs a{
  font-size:11.5px;
  padding:5px 11px;
  border-radius:999px;
  color:var(--muted);
  transition:all .25s ease;
  letter-spacing:.02em;
}
.nav-langs a.active{ background:var(--ink); color:#fff;}
.nav-langs a:hover:not(.active){ color:var(--ink); opacity:1;}

/* PAGE HEADER */
.page-head{
  max-width:760px;
  margin:0 auto;
  padding:clamp(80px,10vw,140px) 24px clamp(48px,6vw,72px);
  text-align:left;
}
.page-head .eyebrow{
  font-family:var(--font-en);
  font-size:12px;
  letter-spacing:.28em;
  text-transform:uppercase;
  color:var(--blue);
  font-weight:500;
  margin-bottom:20px;
}
.page-head h1{
  font-size:clamp(44px, 6vw, 72px);
  font-weight:300;
  letter-spacing:-.02em;
  line-height:1.1;
  margin-bottom:20px;
  color:var(--ink);
}
html[lang="en"] .page-head h1{ font-weight:500; letter-spacing:-.03em;}
.page-head .sub{
  font-size:clamp(18px, 2vw, 22px);
  color:var(--ink-2);
  font-weight:300;
  line-height:1.5;
  margin-bottom:28px;
  max-width:560px;
}
.page-head .dates{
  display:flex; flex-wrap:wrap; gap:20px;
  font-family:var(--font-en);
  font-size:12.5px;
  color:var(--muted);
  letter-spacing:.02em;
  padding-top:20px;
  border-top:1px solid var(--line);
  margin-top:8px;
}
html[lang="zh-CN"] .page-head .dates,
html[lang="zh-TW"] .page-head .dates{ font-family:var(--font-zh);}

/* SUBNAV */
.subnav{
  max-width:760px;
  margin:0 auto;
  padding:0 24px;
  display:flex;
  gap:4px;
  border-bottom:1px solid var(--line);
}
.subnav a{
  padding:14px 18px;
  font-size:13.5px;
  color:var(--muted);
  font-weight:400;
  border-bottom:2px solid transparent;
  margin-bottom:-1px;
  transition:all .2s;
}
.subnav a:hover{ color:var(--ink); opacity:1;}
.subnav a.active{
  color:var(--ink);
  border-bottom-color:var(--ink);
  font-weight:500;
}

/* CONTENT */
.content{
  max-width:760px;
  margin:0 auto;
  padding:clamp(48px,6vw,80px) 24px clamp(80px,10vw,120px);
}
.content section{
  padding:28px 0;
  border-bottom:1px solid var(--line);
}
.content section:last-child{ border-bottom:0;}
.content h2{
  font-size:clamp(22px, 2.4vw, 28px);
  font-weight:500;
  letter-spacing:-.01em;
  color:var(--ink);
  margin-bottom:16px;
  line-height:1.35;
}
.content p{
  font-size:16px;
  color:var(--ink-2);
  font-weight:400;
  line-height:1.75;
  margin-bottom:14px;
}
.content p:last-child{margin-bottom:0;}
.content ul{
  margin:12px 0 16px;
  padding-left:24px;
}
.content li{
  font-size:16px;
  color:var(--ink-2);
  line-height:1.75;
  margin-bottom:8px;
}
.content strong{ color:var(--ink); font-weight:500;}
.content .callout{
  background:var(--blue-soft);
  border-radius:var(--radius);
  padding:20px 24px;
  margin-top:8px;
}
.content .callout p{ margin-bottom:8px; font-size:15px;}
.content .callout p:last-child{ margin-bottom:0;}

/* FOOTER */
.page-foot{
  max-width:760px;
  margin:0 auto;
  padding:40px 24px 56px;
  border-top:1px solid var(--line);
  display:flex; justify-content:space-between; flex-wrap:wrap; gap:16px;
  font-size:12.5px;
  color:var(--muted);
}
.page-foot .foot-links{ display:flex; gap:24px; flex-wrap:wrap;}
.page-foot a{color:var(--muted);}
.page-foot a:hover{color:var(--ink); opacity:1;}

@media (max-width:640px){
  .nav{padding:0 18px;}
  .nav-brand .en{display:none;}
  .subnav{ overflow-x:auto; white-space:nowrap;}
  .subnav a{ padding:14px 14px;}
}