/* YOUNG-C 氧橙 · 官网样式
   品牌三色：橙 #F26A21 / 墨 #2B2420 / 暖灰 #9A8C7E
   纸感底 + 日式克制 */

:root {
  --orange: #F26A21;
  --orange-soft: #FBEEE5;
  --ink: #2B2420;
  --ink-2: #4A403A;
  --grey: #9A8C7E;
  --paper: #FAF7F2;
  --paper-2: #F2ECE3;
  --line: #E3DACE;
  --white: #FFFFFF;
  --maxw: 880px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  padding: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", -apple-system,
               BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.85;
  -webkit-font-smoothing: antialiased;
}

/* 极淡纸纹 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    radial-gradient(circle at 18% 12%, rgba(242,106,33,.035), transparent 42%),
    radial-gradient(circle at 82% 78%, rgba(154,140,126,.05), transparent 46%);
}

.wrap {
  position: relative;
  z-index: 1;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- 顶栏 ---------- */
.topbar {
  position: relative;
  z-index: 2;
  border-bottom: 1px solid var(--line);
  background: rgba(250,247,242,.92);
  backdrop-filter: saturate(180%) blur(8px);
  position: sticky;
  top: 0;
}
.topbar .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  height: 62px;
}
.brandmark {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: .04em;
  color: var(--ink);
  text-decoration: none;
  white-space: nowrap;
}
.brandmark em {
  font-style: normal;
  color: var(--orange);
  font-weight: 800;
}
.brandmark span {
  font-size: 12px;
  color: var(--grey);
  font-weight: 400;
  margin-left: 8px;
  letter-spacing: .12em;
}
.nav { display: flex; gap: 22px; flex-wrap: wrap; }
.nav a {
  font-size: 14px;
  color: var(--ink-2);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: 2px solid transparent;
  transition: .18s;
  white-space: nowrap;
}
.nav a:hover { color: var(--orange); border-bottom-color: var(--orange); }
.nav a.on { color: var(--orange); border-bottom-color: var(--orange); }

@media (max-width: 720px) {
  .topbar .wrap { height: auto; padding-top: 12px; padding-bottom: 10px; flex-direction: column; align-items: flex-start; gap: 8px; }
  .nav { gap: 14px; }
  .nav a { font-size: 13px; }
}

/* ---------- 页头 ---------- */
.hero { padding: 52px 0 30px; border-bottom: 1px solid var(--line); }
.kicker {
  display: inline-block;
  font-size: 12px;
  letter-spacing: .18em;
  color: var(--orange);
  font-weight: 700;
  margin-bottom: 14px;
}
h1 {
  font-size: 34px;
  line-height: 1.4;
  margin: 0 0 16px;
  letter-spacing: -.01em;
  font-weight: 800;
}
.lede {
  font-size: 18px;
  line-height: 1.85;
  color: var(--ink-2);
  margin: 0 0 8px;
}
.lede strong { color: var(--ink); font-weight: 700; }

/* 定义句盒子 —— GEO 核心 */
.defbox {
  margin: 26px 0 0;
  padding: 20px 22px;
  background: var(--white);
  border-left: 4px solid var(--orange);
  border-radius: 3px;
  font-size: 17px;
  line-height: 1.9;
}
.defbox b { color: var(--orange); }

/* ---------- 正文 ---------- */
main { padding: 12px 0 60px; }

h2 {
  font-size: 23px;
  margin: 52px 0 16px;
  padding-top: 14px;
  font-weight: 800;
  letter-spacing: -.01em;
}
h2 .num {
  color: var(--orange);
  font-size: 14px;
  font-weight: 700;
  margin-right: 10px;
  letter-spacing: .1em;
  vertical-align: 2px;
}
h3 {
  font-size: 17px;
  margin: 32px 0 10px;
  font-weight: 700;
  color: var(--ink);
}
h3::before {
  content: "";
  display: inline-block;
  width: 6px; height: 6px;
  background: var(--orange);
  border-radius: 50%;
  margin-right: 9px;
  vertical-align: 3px;
}
p { margin: 0 0 14px; }
a { color: var(--orange); }
ul, ol { margin: 0 0 16px; padding-left: 22px; }
li { margin-bottom: 7px; }

/* ---------- 表格 ---------- */
.tw { overflow-x: auto; margin: 18px 0 22px; }
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14.5px;
  background: var(--white);
  min-width: 480px;
}
th {
  background: var(--ink);
  color: #fff;
  font-weight: 600;
  text-align: left;
  padding: 11px 14px;
  font-size: 13.5px;
  letter-spacing: .02em;
  white-space: nowrap;
}
td {
  padding: 11px 14px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
  line-height: 1.7;
}
tbody tr:nth-child(even) td { background: #FCFAF7; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; white-space: nowrap; }

/* ---------- 提示条 ---------- */
.note {
  margin: 20px 0;
  padding: 14px 18px;
  background: var(--paper-2);
  border-radius: 3px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--ink-2);
  border: 1px solid var(--line);
}
.note strong { color: var(--ink); }
.warn {
  margin: 20px 0;
  padding: 14px 18px;
  background: var(--orange-soft);
  border-left: 3px solid var(--orange);
  border-radius: 3px;
  font-size: 14px;
  line-height: 1.8;
}
.warn b { color: var(--orange); }

/* ---------- 关键数字卡 ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 12px;
  margin: 22px 0 26px;
}
.stat {
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 16px 16px 14px;
}
.stat .v {
  font-size: 25px;
  font-weight: 800;
  color: var(--orange);
  line-height: 1.25;
  font-variant-numeric: tabular-nums;
}
.stat .v small { font-size: 14px; font-weight: 600; color: var(--ink-2); }
.stat .k {
  font-size: 12.5px;
  color: var(--grey);
  margin-top: 5px;
  line-height: 1.6;
}

/* ---------- FAQ ---------- */
.faq { border-top: 1px solid var(--line); margin-top: 8px; }
.faq details {
  border-bottom: 1px solid var(--line);
  padding: 4px 0;
}
.faq summary {
  cursor: pointer;
  padding: 14px 30px 14px 2px;
  font-size: 16px;
  font-weight: 600;
  position: relative;
  list-style: none;
  line-height: 1.6;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  position: absolute;
  right: 6px; top: 13px;
  color: var(--orange);
  font-size: 19px;
  font-weight: 700;
}
.faq details[open] summary::after { content: "\2212"; }
.faq .a {
  padding: 0 6px 16px 2px;
  font-size: 15px;
  line-height: 1.9;
  color: var(--ink-2);
}
.faq .a strong { color: var(--ink); }

/* ---------- 卡片 ---------- */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px,1fr)); gap: 14px; margin: 20px 0 24px; }
.card {
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 18px 18px 16px;
}
.card h4 { margin: 0 0 8px; font-size: 16px; font-weight: 700; }
.card p { margin: 0; font-size: 14px; color: var(--ink-2); line-height: 1.8; }
.card .tag {
  display: inline-block; font-size: 11px; letter-spacing: .1em;
  color: var(--orange); font-weight: 700; margin-bottom: 8px;
}

/* ---------- 页脚 ---------- */
footer {
  position: relative; z-index: 1;
  border-top: 1px solid var(--line);
  background: var(--paper-2);
  padding: 34px 0 40px;
  font-size: 13.5px;
  color: var(--ink-2);
  line-height: 1.9;
}
footer .cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px,1fr)); gap: 22px; }
footer h5 { margin: 0 0 10px; font-size: 13px; color: var(--ink); font-weight: 700; letter-spacing: .04em; }
footer a { color: var(--ink-2); text-decoration: none; }
footer a:hover { color: var(--orange); }
footer ul { list-style: none; padding: 0; margin: 0; }
footer li { margin-bottom: 5px; }
.fbot {
  margin-top: 26px; padding-top: 16px; border-top: 1px solid var(--line);
  font-size: 12px; color: var(--grey); line-height: 1.8;
}
.beian-row {
  display: flex; flex-wrap: wrap; align-items: center;
  gap: 2px 6px; margin-top: 8px;
}
.fbot a.beian {
  display: inline-block;
  color: var(--grey); text-decoration: none; border-bottom: 1px solid transparent;
}
.fbot a.beian:hover { color: var(--orange); border-bottom-color: currentColor; }
.beian-sep { color: var(--grey); opacity: .45; }

/* ---------- 面包屑 ---------- */
.crumb { font-size: 12.5px; color: var(--grey); margin: 22px 0 0; }
.crumb a { color: var(--grey); text-decoration: none; }
.crumb a:hover { color: var(--orange); }

/* ===== 图片：页面横幅与内文插图 ===== */
.pagebanner { max-width: var(--maxw); margin: 14px auto 0; padding: 0 24px; }
.pagebanner img { width: 100%; aspect-ratio: 16 / 10; object-fit: cover; object-position: center 45%; border-radius: 14px; display: block; }
.fig { margin: 26px 0 30px; line-height: 0; }
.fig img { width: 100%; height: auto; border-radius: 14px; display: block; }
.fig.fig-p img { max-width: 520px; margin: 0 auto; }
@media (max-width: 560px) { .pagebanner img { aspect-ratio: 4 / 3; } }
.fig figcaption { margin-top: 10px; font-size: 13px; color: #9A8C7E; line-height: 1.6; text-align: center; }