:root{
  --bg:#f6f7f9;
  --card:#ffffff;
  --ink:#1a2233;
  --muted:#6b7280;
  --brand:#0f5bd7;
  --brand-dark:#0a47a8;
  --accent:#0aa06e;
  --line:#e7eaf0;
  --radius:14px;
  --shadow:0 1px 3px rgba(20,30,55,.06),0 6px 20px rgba(20,30,55,.05);
  --nav-h:64px;
}
*{box-sizing:border-box;margin:0;padding:0;}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.7;
}
a{text-decoration:none;color:inherit;}
img{max-width:100%;display:block;}
.wrap{max-width:1280px;margin:0 auto;padding:0 24px;}

/* 超大屏（2K/4K）：放宽内容宽度、网格列数增加、字体适度放大 */
@media(min-width:1600px){
  .wrap{max-width:1560px;}
  /* 字体放大：正文 + 标题 */
  body{font-size:17px;}
  .sec-head h2{font-size:26px;}
  .card h2,section h2{font-size:22px;}
  /* 网格列数增加，铺满宽屏 */
  .grid-3{grid-template-columns:repeat(4,1fr);}
  .grid-4{grid-template-columns:repeat(5,1fr);}
}

/* 国旗图片（替换 emoji 国旗，带 alt） */
.flag-img{display:inline-block;border-radius:3px;box-shadow:0 1px 2px rgba(0,0,0,.18);vertical-align:middle;object-fit:cover;flex:none;}

/* 顶部通知条 */
.topbar{background:var(--brand-dark);color:#fff;font-size:13px;}
.topbar .wrap{display:flex;justify-content:space-between;align-items:center;height:36px;}
.topbar a{color:#cfe0ff;margin-left:16px;}

/* 导航 */
header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:50;}
.nav{display:flex;align-items:center;height:var(--nav-h);gap:24px;}
.logo{display:flex;align-items:center;gap:10px;font-weight:800;font-size:22px;color:var(--brand);}
.logo .dot{width:10px;height:10px;background:var(--accent);border-radius:50%;}
.logo img{height:52px;width:auto;display:block;}
@media(max-width:560px){.logo img{height:36px;}}
nav{display:flex;gap:35px;margin-left:auto;font-size:16.5px;font-weight:500;}
nav a{color:var(--ink);position:relative;padding:4px 0;white-space:nowrap;}
nav a:hover{color:var(--brand);}
nav a.active{color:var(--brand);}
nav a.active::after{content:"";position:absolute;left:0;right:0;bottom:-4px;height:3px;background:var(--brand);border-radius:2px;}
.nav-cta a{display:inline-block;padding:9px 18px;background:var(--brand);color:#fff;border-radius:8px;font-size:15px;font-weight:600;white-space:nowrap;}
.nav-cta a:hover{background:var(--brand-dark);}

/* 汉堡菜单按钮（移动端） */
.nav-toggle{display:none;flex-direction:column;justify-content:center;gap:4px;width:40px;height:40px;padding:8px;cursor:pointer;border-radius:8px;}
.nav-toggle span{display:block;height:2px;width:100%;background:var(--ink);border-radius:2px;transition:.2s;}
.nav-toggle-input:checked ~ .nav-toggle span:nth-child(1){transform:translateY(6px) rotate(45deg);}
.nav-toggle-input:checked ~ .nav-toggle span:nth-child(2){opacity:0;}
.nav-toggle-input:checked ~ .nav-toggle span:nth-child(3){transform:translateY(-6px) rotate(-45deg);}

/* 专业术语内链（指向百科） */
.term-link{color:var(--brand);border-bottom:1px dashed #9db8e8;text-decoration:none;transition:.15s;}
.term-link:hover{color:var(--brand-dark);border-bottom:1px solid var(--brand);}

/* 信息时效标注条（详情页正文与页脚之间） */
.info-meta{max-width:1280px;margin:0 auto 20px;padding:0 24px;display:flex;flex-wrap:wrap;gap:6px 20px;font-size:12.5px;color:var(--muted);}
.info-meta span{display:inline-flex;align-items:center;gap:4px;}
.info-meta .im-effective{color:#0f5bd7;font-weight:600;}
.info-meta .im-updated{color:#33405a;font-weight:600;}
.info-meta .im-note{color:#b45309;background:#fef7e6;padding:2px 10px;border-radius:12px;}
.crumb-wrap{margin-bottom:8px;}
.crumb{font-size:13px;color:var(--muted);padding:16px 0 0;}
.crumb a{color:var(--muted);}
.crumb a:hover{color:var(--brand);}
.crumb span{color:var(--ink);}

/* 区块标题 */
.section{padding:40px 0;}
.sec-head{display:flex;align-items:flex-end;justify-content:space-between;margin-bottom:20px;}
.sec-head h2{font-size:23px;font-weight:700;}
.sec-head h2 em{font-style:normal;color:var(--brand);}
.sec-head .sub{font-size:14px;color:var(--muted);margin-top:4px;}
.sec-head .more{font-size:14px;color:var(--brand);font-weight:500;}

/* 卡片网格 */
.grid{display:grid;gap:16px;}
.grid-3{grid-template-columns:repeat(3,1fr);}
.grid-2{grid-template-columns:1fr 1fr;}
.grid-4{grid-template-columns:repeat(4,1fr);}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);}

/* 标签 */
.tag{display:inline-block;font-size:12px;font-weight:600;color:var(--brand);background:#eaf1ff;padding:2px 10px;border-radius:20px;}
.tag.green{color:#0a7a55;background:#e3f7ee;}

/* 按钮 */
.btn{display:inline-block;background:var(--brand);color:#fff;padding:12px 26px;border-radius:10px;font-weight:600;font-size:15px;transition:.15s;}
.btn:hover{background:var(--brand-dark);}
.btn.green{background:var(--accent);}
.btn.green:hover{background:#0d7f59;}
.btn.ghost{background:transparent;border:1.5px solid var(--brand);color:var(--brand);}
.btn.ghost:hover{background:#eaf1ff;}

/* 两栏正文布局 */
.layout{display:grid;grid-template-columns:1fr 320px;gap:28px;align-items:start;}

/* 页脚 */
footer{background:#12192b;color:#9aa5bd;margin-top:20px;}
.f-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr 1fr;gap:30px;padding:48px 0 32px;}
footer h5{color:#fff;font-size:15px;margin-bottom:14px;font-weight:600;}
footer a{display:block;font-size:13.5px;color:#9aa5bd;margin-bottom:8px;}
footer a:hover{color:#fff;}
.f-brand{display:flex;align-items:center;gap:10px;font-size:20px;font-weight:800;color:#fff;margin-bottom:10px;}
.f-brand img{height:36px;width:auto;display:block;}
.f-slogan{color:#e8b64c;font-size:14px;font-weight:600;letter-spacing:2px;margin-bottom:12px;}
.f-about p{font-size:13.5px;line-height:1.7;max-width:300px;}
.f-resource{margin-top:14px;display:flex;flex-wrap:wrap;gap:4px;}
.f-resource a{display:inline-block;font-size:12.5px;color:#9aa5bd;background:#1c2540;padding:4px 12px;border-radius:14px;margin-bottom:6px;}
.f-resource a:hover{color:#fff;background:#26335a;}
.disclaim{border-top:1px solid #26324d;padding:18px 0;font-size:12px;color:#6b7895;text-align:center;}

@media(max-width:900px){
  .layout{grid-template-columns:1fr;}
  .grid-4,.grid-3{grid-template-columns:repeat(2,1fr);}
  .grid-2{grid-template-columns:1fr;}
  .f-grid{grid-template-columns:1fr 1fr;}
  /* 移动端导航：汉堡菜单 + 下拉展开 */
  .nav{position:relative;gap:16px;}
  .nav-toggle{display:flex;margin-left:auto;}
  .nav-cta{margin-left:auto;}
  .nav-toggle{order:3;}
  .nav-cta{order:4;}
  nav{display:none;position:absolute;top:var(--nav-h);left:0;right:0;background:var(--card);flex-direction:column;gap:0;padding:8px 16px 16px;border-bottom:1px solid var(--line);box-shadow:0 12px 24px rgba(20,30,55,.12);z-index:49;}
  .nav-toggle-input:checked ~ nav{display:flex;}
  nav a{padding:12px 8px;border-bottom:1px solid var(--line);font-size:16px;}
  nav a:last-child{border-bottom:none;}
  nav a.active::after{display:none;}
}
@media(max-width:560px){
  .grid-4,.grid-3{grid-template-columns:1fr;}
  .f-grid{grid-template-columns:1fr;}
}