/* ============ 2026 SEO 指南 · 编辑部纸刊风格 ============ */
:root {
  --paper: #f6f1e7;
  --paper-deep: #ece4d3;
  --ink: #1c180f;
  --ink-soft: #57503f;
  --accent: #d43d19;
  --accent-deep: #a52c0e;
  --green: #2f5d3a;
  --gold: #b98a2f;
  --rule: #c9bfa8;
  --serif: "Noto Serif SC", "Songti SC", serif;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--sans);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.85;
  font-size: 16.5px;
  position: relative;
}
/* 纸张噪点 */
body::before {
  content: "";
  position: fixed; inset: 0;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)' opacity='0.05'/%3E%3C/svg%3E");
  pointer-events: none;
  z-index: 999;
}
a { color: var(--accent-deep); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--accent); }

/* ---------- 顶栏 ---------- */
.masthead {
  border-bottom: 3px double var(--ink);
  padding: 18px 5vw 14px;
  display: flex; align-items: baseline; justify-content: space-between; flex-wrap: wrap; gap: 10px;
  background: var(--paper);
}
.masthead .brand {
  font-family: var(--serif); font-weight: 900; font-size: 22px; letter-spacing: 2px;
  color: var(--ink); text-decoration: none;
}
.masthead .brand em { color: var(--accent); font-style: normal; }
.masthead .issue { font-size: 12.5px; letter-spacing: 3px; color: var(--ink-soft); }
nav.toc {
  padding: 10px 5vw;
  border-bottom: 1px solid var(--rule);
  display: flex; flex-wrap: wrap; gap: 4px 22px;
  font-size: 13.5px;
  background: var(--paper);
  position: sticky; top: 0; z-index: 50;
  box-shadow: 0 1px 0 var(--paper-deep);
}
nav.toc a { color: var(--ink-soft); text-decoration: none; letter-spacing: 1px; }
nav.toc a:hover, nav.toc a.active { color: var(--accent); }
nav.toc a::before { content: "◆ "; color: var(--gold); font-size: 9px; vertical-align: 2px; }

/* ---------- 页头大标题 ---------- */
.hero { padding: 9vh 5vw 6vh; border-bottom: 1px solid var(--rule); }
.kicker {
  display: inline-block; font-size: 12.5px; letter-spacing: 4px;
  color: var(--paper); background: var(--ink); padding: 4px 14px; margin-bottom: 26px;
}
.kicker.red { background: var(--accent); }
h1.display {
  font-family: var(--serif); font-weight: 900;
  font-size: clamp(38px, 6.2vw, 74px);
  line-height: 1.18; letter-spacing: 1px; max-width: 20em;
}
h1.display .hl { color: var(--accent); position: relative; }
.standfirst {
  margin-top: 26px; max-width: 46em; font-size: 18px; color: var(--ink-soft);
  border-left: 4px solid var(--accent); padding-left: 18px;
}
.byline { margin-top: 22px; font-size: 13px; letter-spacing: 2px; color: var(--ink-soft); }
.byline b { color: var(--ink); }

/* ---------- 正文 ---------- */
main.body { max-width: 880px; margin: 0 auto; padding: 60px 5vw 40px; }
section.chapter { margin-bottom: 72px; }
.chap-num {
  font-family: var(--serif); font-size: 15px; letter-spacing: 5px; color: var(--accent);
  margin-bottom: 8px; font-weight: 700;
}
h2 {
  font-family: var(--serif); font-weight: 900; font-size: clamp(26px, 3.4vw, 38px);
  line-height: 1.3; margin-bottom: 22px;
}
h3 {
  font-family: var(--serif); font-size: 21px; margin: 34px 0 12px;
  padding-left: 14px; border-left: 5px solid var(--gold);
}
p { margin-bottom: 18px; }
main.body ul, main.body ol { padding-left: 1.6em; margin-bottom: 20px; }
main.body li { margin-bottom: 10px; }
main.body li::marker { color: var(--accent); }
strong { background: linear-gradient(transparent 62%, rgba(212,61,25,.22) 62%); }

/* 引言块 */
blockquote {
  margin: 30px 0; padding: 22px 26px; background: var(--paper-deep);
  border: 1px solid var(--rule); border-left: 6px solid var(--ink);
  font-family: var(--serif); font-size: 17.5px;
}
blockquote .who { display: block; margin-top: 10px; font-size: 13px; color: var(--ink-soft); font-family: var(--sans); letter-spacing: 1px; }

/* 数据卡片 */
.stat-row { display: flex; flex-wrap: wrap; gap: 18px; margin: 30px 0; }
.stat {
  flex: 1 1 180px; border: 1.5px solid var(--ink); padding: 18px 20px 14px;
  background: var(--paper); box-shadow: 5px 5px 0 var(--ink);
}
.stat .n { font-family: var(--serif); font-weight: 900; font-size: 34px; color: var(--accent); line-height: 1.1; }
.stat .t { font-size: 13px; color: var(--ink-soft); margin-top: 6px; }

/* 表格 */
table { width: 100%; border-collapse: collapse; margin: 26px 0; font-size: 15px; }
th { background: var(--ink); color: var(--paper); text-align: left; padding: 10px 14px; font-weight: 600; letter-spacing: 1px; }
td { border: 1px solid var(--rule); padding: 10px 14px; vertical-align: top; }
tr:nth-child(even) td { background: var(--paper-deep); }

/* 步骤清单 */
ol.steps { counter-reset: step; list-style: none; padding: 0; }
ol.steps li {
  counter-increment: step; position: relative; padding: 16px 18px 16px 66px;
  border-bottom: 1px dashed var(--rule); margin: 0;
}
ol.steps li::before {
  content: counter(step, decimal-leading-zero);
  position: absolute; left: 0; top: 14px;
  font-family: var(--serif); font-weight: 900; font-size: 26px; color: var(--accent);
}
ol.steps li b { display: block; font-family: var(--serif); font-size: 17.5px; margin-bottom: 4px; }

/* FAQ */
.faq details { border-bottom: 1px solid var(--rule); padding: 14px 4px; }
.faq summary { font-family: var(--serif); font-weight: 700; font-size: 17px; cursor: pointer; }
.faq summary::marker { color: var(--accent); }
.faq details p { margin: 12px 0 4px; color: var(--ink-soft); }

/* 交叉链接 */
.crosslinks { border-top: 3px double var(--ink); padding: 40px 0 10px; }
.crosslinks h2 { font-size: 22px; }
.link-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 16px; margin-top: 20px; }
.link-cards a {
  display: block; text-decoration: none; color: var(--ink);
  border: 1.5px solid var(--ink); padding: 18px 18px 14px; background: var(--paper);
  transition: transform .18s ease, box-shadow .18s ease;
}
.link-cards a:hover { transform: translate(-3px,-3px); box-shadow: 5px 5px 0 var(--accent); color: var(--ink); }
.link-cards .no { font-family: var(--serif); color: var(--accent); font-weight: 900; font-size: 13px; letter-spacing: 2px; }
.link-cards .ti { font-family: var(--serif); font-weight: 900; font-size: 18px; margin: 6px 0; }
.link-cards .de { font-size: 13px; color: var(--ink-soft); line-height: 1.6; }

/* 页脚 */
footer {
  margin-top: 70px; border-top: 3px double var(--ink);
  padding: 26px 5vw 40px; font-size: 13px; color: var(--ink-soft);
  display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px;
}
footer nav a { margin-right: 16px; color: var(--ink-soft); }

/* 首页目录（期刊风） */
.cover-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 0; border-top: 1px solid var(--ink); }
.cover-item {
  padding: 30px 26px 26px; border-bottom: 1px solid var(--ink); border-right: 1px solid var(--ink);
  text-decoration: none; color: var(--ink); position: relative; background: var(--paper);
  transition: background .2s ease;
}
.cover-item:hover { background: var(--paper-deep); }
.cover-item .no { font-family: var(--serif); font-weight: 900; font-size: 15px; color: var(--accent); letter-spacing: 3px; }
.cover-item h2 { font-size: 24px; margin: 8px 0 10px; }
.cover-item p { font-size: 14px; color: var(--ink-soft); margin: 0; }
.cover-item .heat {
  display: inline-block; margin-top: 14px; font-size: 12px; letter-spacing: 1px;
  color: var(--accent-deep); border: 1px solid var(--accent-deep); padding: 2px 10px;
}
.cover-item .go { position: absolute; right: 20px; top: 30px; font-size: 20px; color: var(--ink); transition: transform .2s; }
.cover-item:hover .go { transform: translateX(5px); color: var(--accent); }

/* 入场动画 */
@keyframes rise { from { opacity: 0; transform: translateY(16px); } to { opacity: 1; transform: none; } }
.hero > *, .cover-item, section.chapter > * { animation: rise .6s ease both; }
.hero > *:nth-child(2) { animation-delay: .08s; } .hero > *:nth-child(3) { animation-delay: .16s; } .hero > *:nth-child(4) { animation-delay: .24s; }
@media (prefers-reduced-motion: reduce) { * { animation: none !important; } }

@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .masthead { flex-direction: column; gap: 4px; }
}