/* 考研408计算机网络带学 - 公共样式（侧边栏布局版） */
:root {
  --blue: #8b5cf6;
  --blue-deep: #7c3aed;
  --blue-dark: #6d28d9;
  --sidebar-bg: #32265e;
  --sidebar-bg2: #281d4e;
  --sidebar-text: #ddd3f2;
  --sidebar-dim: #a99ccf;
  --topbar-h: 58px;
  --bg: #f6f4fc;
  --card: #ffffff;
  --text: #2a2438;
  --text-light: #6f6a80;
  --border: #e6e1f2;
  --primary: #7c3aed;
  --primary-light: #f5f3ff;
  --accent: #dc2626;
  --green: #059669;
  --green-light: #ecfdf5;
  --amber: #d97706;
  --amber-light: #fffbeb;
  --radius: 14px;
  --shadow: 0 1px 3px rgba(60, 40, 100, .06), 0 4px 14px rgba(60, 40, 100, .05);
}
html[data-theme="dark"] {
  --bg: #161226;
  --card: #241d3d;
  --text: #ece7f8;
  --text-light: #a89ec4;
  --border: #3d3459;
  --primary: #c4b5fd;
  --primary-light: #3b2a63;
  --green: #34d399;
  --green-light: #064e3b33;
  --amber-light: #78350f33;
  --sidebar-bg: #1a1430;
  --sidebar-bg2: #201838;
  --shadow: 0 1px 3px rgba(0, 0, 0, .4);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; font-size: 16px; }
body {
  margin: 0;
  font-family: "Microsoft YaHei", "PingFang SC", "Segoe UI", system-ui, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.85;
  font-size: 1rem;
}

/* ============ 顶部导航 ============ */
.topbar {
  position: sticky; top: 0; z-index: 200;
  height: var(--topbar-h);
  background: linear-gradient(90deg, #6d28d9 0%, #7c3aed 45%, #a78bfa 100%);
  color: #fff;
  display: flex; align-items: center; gap: 14px;
  padding: 0 16px;
  box-shadow: 0 2px 8px rgba(124, 58, 237, .35);
}
.topbar .burger {
  display: none;
  background: rgba(255,255,255,.14); color: #fff; border: none;
  width: 34px; height: 34px; border-radius: 8px; font-size: 17px; cursor: pointer;
}
.topbar .brand {
  font-weight: 800; font-size: 1.12rem; color: #fff; text-decoration: none;
  white-space: nowrap; letter-spacing: .5px;
}
.topbar .tagline { font-size: .78rem; opacity: .9; white-space: nowrap; }
.topbar .spacer { flex: 1; }
.searchbox { position: relative; width: min(380px, 34vw); }
.searchbox input {
  width: 100%; height: 36px;
  border: 1px solid rgba(255,255,255,.35); border-radius: 999px;
  background: rgba(255,255,255,.16); color: #fff;
  padding: 0 16px 0 38px; font-size: .88rem; outline: none;
}
.searchbox input::placeholder { color: rgba(255,255,255,.75); }
.searchbox input:focus { background: rgba(255,255,255,.26); }
.searchbox .s-ico {
  position: absolute; left: 13px; top: 50%; transform: translateY(-50%);
  font-size: .85rem; opacity: .85; pointer-events: none;
}
.search-results {
  position: absolute; top: 42px; left: 0; right: 0;
  background: var(--card); color: var(--text);
  border-radius: 10px; box-shadow: 0 10px 30px rgba(15,23,42,.25);
  overflow: hidden; display: none; max-height: 60vh; overflow-y: auto;
}
.search-results.open { display: block; }
.search-results a {
  display: block; padding: 9px 14px; text-decoration: none; color: var(--text);
  border-bottom: 1px solid var(--border); font-size: .88rem;
}
.search-results a:last-child { border-bottom: none; }
.search-results a:hover { background: var(--primary-light); }
.search-results a .sr-sub { color: var(--text-light); font-size: .78rem; margin-left: 6px; }
.search-results .sr-none { padding: 10px 14px; color: var(--text-light); font-size: .85rem; }
.topbtn {
  width: 34px; height: 34px; border-radius: 8px; border: 1px solid rgba(255,255,255,.4);
  background: rgba(255,255,255,.14); color: #fff;
  font-size: .82rem; font-weight: 700; cursor: pointer; flex: none;
}
.topbtn:hover { background: rgba(255,255,255,.28); }

/* ============ 布局 ============ */
.layout { display: flex; min-height: calc(100vh - var(--topbar-h)); }

/* ============ 侧边栏 ============ */
.sidebar {
  width: 284px; flex: none;
  background: linear-gradient(180deg, var(--sidebar-bg) 0%, var(--sidebar-bg2) 100%);
  color: var(--sidebar-text);
  position: sticky; top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  padding: 14px 12px 40px;
  scrollbar-width: thin; scrollbar-color: #4c3a7d transparent;
}
.sidebar::-webkit-scrollbar { width: 6px; }
.sidebar::-webkit-scrollbar-thumb { background: #4c3a7d; border-radius: 3px; }
.side-brand {
  border: 1.5px solid #5847a0; border-radius: 12px;
  text-align: center; padding: 14px 10px 12px; margin: 2px 4px 16px;
  background: rgba(255,255,255,.04);
}
.side-brand .sb-title {
  font-size: 1.35rem; font-weight: 800; color: #fff; letter-spacing: 6px;
  font-family: "STZhongsong", "SimSun", serif;
}
.side-brand .sb-line { font-size: .78rem; color: var(--sidebar-dim); margin-top: 4px; line-height: 1.6; }
.side-home {
  display: flex; align-items: center; gap: 8px;
  color: var(--sidebar-text); text-decoration: none;
  padding: 8px 12px; border-radius: 8px; font-size: .92rem; margin: 0 4px 10px;
}
.side-home:hover { background: rgba(255,255,255,.08); }
.side-group { margin-bottom: 6px; }
.side-head {
  display: flex; align-items: center; gap: 8px;
  padding: 9px 10px; margin: 0 2px;
  color: #dbe4f7; font-size: .88rem; font-weight: 700;
  cursor: pointer; user-select: none; border-radius: 8px;
  list-style: none;
}
.side-head:hover { background: rgba(255,255,255,.07); }
.side-head .cnt {
  margin-left: auto; font-size: .72rem; font-weight: 600;
  background: rgba(255,255,255,.12); color: var(--sidebar-dim);
  border-radius: 999px; padding: 1px 9px;
}
.side-head .cnt.done { background: #14532d; color: #86efac; }
.side-head .chev { font-size: .62rem; transition: transform .18s; color: var(--sidebar-dim); }
.side-group.open > .side-head .chev { transform: rotate(90deg); }
.side-items { display: none; padding: 2px 0 6px; }
.side-group.open > .side-items { display: block; }
.side-items a {
  display: flex; align-items: center; gap: 6px;
  color: var(--sidebar-text); text-decoration: none;
  font-size: .87rem; padding: 7px 12px 7px 20px; border-radius: 8px;
  margin: 1px 4px;
}
.side-items a:hover { background: rgba(255,255,255,.08); color: #fff; }
.side-items a.active { background: var(--blue); color: #fff; font-weight: 600; }
.side-items a .dot { font-size: .6rem; opacity: .55; flex: none; }
.side-items a.visited:not(.active) .dot { color: #4ade80; opacity: 1; }
.side-mask { display: none; }

/* ============ 主内容 ============ */
main.content {
  flex: 1; min-width: 0;
  max-width: 1080px; margin: 0 auto;
  padding: 26px 28px 70px;
}
.crumbs { font-size: .84rem; color: var(--text-light); margin-bottom: 16px; }
.crumbs a { color: var(--text-light); text-decoration: none; }
.crumbs a:hover { color: var(--primary); }

h1.page-title {
  font-size: 1.85rem; line-height: 1.35; margin: 4px 0 6px; color: var(--text);
  padding-bottom: 12px; border-bottom: 3px solid var(--primary);
}
.subtitle { color: var(--text-light); font-size: .9rem; margin-bottom: 24px; }
h2.sec {
  font-size: 1.42rem; margin: 42px 0 14px; color: var(--primary);
  border-left: 5px solid var(--primary); padding-left: 12px; line-height: 1.4;
}
h3.sub { font-size: 1.14rem; margin: 30px 0 10px; color: var(--text); }
h4 { font-size: 1.02rem; margin: 20px 0 8px; }
p { margin: 10px 0; }
a { color: var(--primary); }
strong { color: var(--text); }
ol li, ul li { margin: 4px 0; }

/* 提示框 */
.box {
  background: var(--card); border: 1px solid var(--border);
  border-radius: 10px; padding: 13px 18px; margin: 16px 0;
}
.box .box-title { font-weight: 700; margin-bottom: 6px; display: flex; align-items: center; gap: 8px; }
.box.concept { border-left: 4px solid var(--primary); background: var(--primary-light); }
.box.tip { border-left: 4px solid var(--green); background: var(--green-light); }
.box.warn { border-left: 4px solid var(--amber); background: var(--amber-light); }
.box.exam { border-left: 4px solid var(--accent); background: #fef2f2; }
html[data-theme="dark"] .box.exam { background: #7f1d1d33; }
.box.sup { border-left: 4px solid #8b5cf6; background: #f8f5ff; }
html[data-theme="dark"] .box.sup { background: #8b5cf620; }
.box.sup .box-title { color: #6d28d9; }
html[data-theme="dark"] .box.sup .box-title { color: #c4b5fd; }
.badge.sup { background: #8b5cf6; color: #fff; }

/* 徽标 */
.badge {
  display: inline-block; font-size: .72rem; font-weight: 700; line-height: 1;
  padding: 4px 8px; border-radius: 999px; vertical-align: 2px; white-space: nowrap;
}
.badge.kao { background: var(--accent); color: #fff; }
.badge.ext { background: #7c3aed; color: #fff; }
.badge.imp { background: var(--amber); color: #fff; }

/* 插图 */
figure.fig { margin: 22px auto; text-align: center; }
figure.fig img {
  max-width: 100%; height: auto; border: 1px solid var(--border);
  border-radius: 8px; background: #fff; padding: 6px;
  box-shadow: 0 2px 8px rgba(0,0,0,.06);
}
figure.fig figcaption { font-size: .84rem; color: var(--text-light); margin-top: 8px; }

/* 表格 */
table.tbl {
  border-collapse: collapse; width: 100%; margin: 16px 0; background: var(--card);
  font-size: .9rem; color: var(--text);
}
table.tbl th, table.tbl td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
table.tbl th { background: var(--primary-light); color: var(--primary); font-weight: 700; }
html[data-theme="dark"] table.tbl th { color: #ddd3fe; }

/* 公式 */
.formula {
  background: var(--card); border: 1px dashed var(--border); border-radius: 8px;
  padding: 10px 16px; margin: 14px 0; overflow-x: auto; text-align: center;
}

/* 习题 */
.quiz-item {
  background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 15px 20px; margin: 18px 0;
}
/* 习题配图（裸 img）：约束宽度、居中、卡片观感 */
.quiz-item img, main.content img {
  max-width: 100%; height: auto;
}
.quiz-item p > img:only-child, .quiz-item img {
  display: block; margin: 12px auto;
  border: 1px solid var(--border); border-radius: 8px;
  background: #fff; padding: 4px;
  box-shadow: 0 2px 8px rgba(0,0,0,.06);
}
.quiz-item td img, .quiz-item th img { margin: 4px auto; }
/* KaTeX 长公式横向滚动兜底 */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 3px 0; }

/* ============ 自测模式（习题页） ============ */
.st-launch { display: flex; align-items: center; gap: 14px; margin: 18px 0 4px; }
.st-launch .st-go {
  background: linear-gradient(135deg, #7c3aed, #a78bfa); color: #fff;
  border: none; border-radius: 999px; padding: 10px 26px;
  font-size: .95rem; font-weight: 700; cursor: pointer;
  box-shadow: 0 4px 12px rgba(124, 58, 237, .35);
}
.st-launch .st-go:hover { filter: brightness(1.08); }
.st-launch .st-best { font-size: .85rem; color: var(--text-light); }
.st-bar {
  position: fixed; left: 50%; transform: translateX(-50%);
  bottom: 18px; z-index: 300;
  background: #1e293b; color: #e2e8f0;
  border: 1px solid #475569; border-radius: 999px;
  padding: 9px 18px; font-size: .88rem; font-weight: 600;
  box-shadow: 0 8px 26px rgba(0, 0, 0, .35);
  display: flex; align-items: center; gap: 10px; white-space: nowrap;
}
.st-bar .st-exit {
  background: rgba(255,255,255,.12); color: #fff; border: 1px solid #64748b;
  border-radius: 999px; padding: 3px 12px; cursor: pointer; font-size: .8rem;
}
.st-opt { cursor: pointer; border-radius: 6px; padding: 2px 8px; margin: 2px -8px; transition: background .12s; }
.st-opt:hover { background: var(--primary-light); }
.st-pick { outline: 2px solid #8b5cf6; outline-offset: -2px; }
.st-right { background: #dcfce6; border-radius: 6px; }
.st-right::after { content: " ✓"; color: var(--green); font-weight: 700; }
.st-wrong { background: #fee2e2; border-radius: 6px; }
.st-wrong::after { content: " ✗"; color: var(--accent); font-weight: 700; }
html[data-theme="dark"] .st-right { background: #14532d66; }
html[data-theme="dark"] .st-wrong { background: #7f1d1d66; }
.st-skip {
  font-size: .8rem; color: var(--amber); background: var(--amber-light);
  border: 1px dashed var(--amber); border-radius: 8px; padding: 4px 12px; margin: 10px 0;
}
@media (max-width: 640px) { .st-bar { font-size: .78rem; padding: 8px 12px; bottom: 10px; max-width: 96vw; overflow-x: auto; } }
.quiz-item .q-no { font-weight: 700; color: var(--primary); }
.quiz-item .q-src { font-size: .76rem; color: #94a3b8; margin-left: 8px; }
.choices { margin: 8px 0 4px; padding-left: 8px; list-style: none; }
.choices li { margin: 3px 0; }
details.ans {
  margin-top: 10px; border: 1px solid var(--border); border-radius: 8px;
  background: var(--green-light); overflow: hidden;
}
details.ans summary {
  cursor: pointer; font-weight: 700; color: var(--green);
  padding: 9px 14px; user-select: none; list-style: none;
}
details.ans summary::before { content: "▸ "; }
details.ans[open] summary::before { content: "▾ "; }
details.ans .ans-body { padding: 4px 16px 14px; border-top: 1px dashed var(--border); }
details.ans .ans-key { font-weight: 700; color: var(--accent); }

/* 上/下一页 */
.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 46px; }
.pager a {
  flex: 1; text-decoration: none; border: 1px solid var(--border);
  background: var(--card); border-radius: var(--radius); padding: 12px 16px;
  color: var(--text);
}
.pager a:hover { border-color: var(--primary); color: var(--primary); }
.pager .prev { text-align: left; }
.pager .next { text-align: right; }
.pager .label { font-size: .76rem; color: var(--text-light); display: block; }

/* ============ 首页 ============ */
.hero {
  background: var(--card); border: 1px solid var(--border); border-radius: 16px;
  padding: 30px 30px 24px; margin-bottom: 26px; position: relative; overflow: hidden;
  box-shadow: var(--shadow);
}
.hero::before {
  content: ""; position: absolute; inset: 0 0 auto 0; height: 5px;
  background: linear-gradient(90deg, #7c3aed, #a78bfa, #c4b5fd);
}
.hero h1 { margin: 2px 0 8px; font-size: 1.72rem; line-height: 1.4; color: var(--text); }
.hero .hero-desc { color: var(--text-light); font-size: .95rem; margin: 6px 0; }
.motto {
  border: 1px solid var(--border); background: var(--primary-light);
  border-radius: 10px; padding: 12px 18px; margin: 16px 0 6px;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
}
.motto .m-main {
  font-family: "STZhongsong", "KaiTi", "SimSun", serif;
  font-size: 1.18rem; color: var(--primary); font-weight: 700; letter-spacing: 3px;
}
.motto .m-sub { font-size: .8rem; color: var(--text-light); }
.checkin-row {
  border: 1.5px dashed var(--primary); border-radius: 12px;
  padding: 12px 18px; margin: 16px 0 4px;
  display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
  background: var(--card);
}
.btn-checkin {
  background: linear-gradient(135deg, #7c3aed, #a78bfa); color: #fff;
  border: none; border-radius: 999px; padding: 10px 26px;
  font-size: .95rem; font-weight: 700; cursor: pointer;
  box-shadow: 0 4px 12px rgba(124, 58, 237, .35);
}
.btn-checkin:disabled { opacity: .55; cursor: default; box-shadow: none; }
.checkin-row .ci-stat { font-size: .92rem; color: var(--text); }
.checkin-row .ci-stat b { color: var(--primary); font-size: 1.05rem; }
.progressbar {
  height: 10px; border-radius: 999px; background: var(--border); overflow: hidden; flex: 1;
  min-width: 120px;
}
.progressbar i {
  display: block; height: 100%; width: 0;
  background: linear-gradient(90deg, #22c55e, #4ade80); border-radius: 999px;
  transition: width .4s;
}
.tagline-row { font-size: .88rem; color: var(--text-light); margin: 14px 0 0; }
.tagline-row b { color: var(--text); }

.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 18px; margin: 18px 0 8px; }
.card {
  background: var(--card); border: 1px solid var(--border); border-top: 4px solid var(--blue);
  border-radius: 12px; padding: 18px 20px; text-decoration: none; color: var(--text); display: flex;
  flex-direction: column; gap: 6px; transition: box-shadow .15s, transform .15s;
  box-shadow: var(--shadow); position: relative;
}
.card:hover { box-shadow: 0 10px 26px rgba(124, 58, 237, .16); transform: translateY(-3px); }
.card .card-ico { font-size: 1.7rem; }
.card .card-stat { position: absolute; top: 16px; right: 18px; font-size: .76rem; color: var(--amber); font-weight: 600; }
.card .card-title { font-weight: 800; color: var(--text); font-size: 1.08rem; margin-top: 4px; }
.card .card-desc { font-size: .84rem; color: var(--text-light); flex: 1; }
.card .card-btn {
  align-self: flex-start; margin-top: 8px;
  background: var(--blue); color: #fff; border-radius: 8px;
  font-size: .86rem; font-weight: 700; padding: 6px 16px;
}
.card:hover .card-btn { background: var(--blue-deep); }

.toc-line { display: flex; justify-content: space-between; border-bottom: 1px dashed var(--border); padding: 5px 2px; font-size: .9rem; }
.toc-line a { text-decoration: none; }
.toc-line a:visited { color: var(--green); }
.toc-line .pg { color: #94a3b8; font-size: .8rem; white-space: nowrap; }

/* 章节地图（导学/速记页知识框架链） */
.map-flow { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 14px 0; }
.map-node {
  background: var(--primary-light); border: 1.5px solid var(--primary);
  color: var(--primary); font-weight: 600; border-radius: 8px; padding: 6px 12px;
  font-size: .86rem; text-decoration: none;
}
.map-node:hover { background: var(--primary); color: #fff; }
.map-arrow { color: #94a3b8; font-weight: 700; }

footer.site-footer {
  border-top: 1px solid var(--border); margin-top: 40px; padding: 20px 16px 34px;
  text-align: center; color: #94a3b8; font-size: .8rem;
}

/* 目录框（全站目录） */
.tocbox { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 6px 20px 14px; }

@media (max-width: 960px) {
  .topbar .tagline { display: none; }
  .searchbox { width: min(300px, 40vw); }
  .topbar .burger { display: block; }
  .sidebar {
    position: fixed; left: 0; top: var(--topbar-h); z-index: 150;
    transform: translateX(-105%); transition: transform .22s ease;
    box-shadow: 8px 0 30px rgba(0,0,0,.3);
  }
  body.side-open .sidebar { transform: translateX(0); }
  body.side-open .side-mask {
    display: block; position: fixed; inset: var(--topbar-h) 0 0 0; z-index: 140;
    background: rgba(15, 23, 42, .45);
  }
  main.content { padding: 20px 16px 60px; }
  h1.page-title { font-size: 1.45rem; }
  .pager { flex-direction: column; }
  .pager .next { text-align: left; }
}
@media (max-width: 640px) {
  /* 顶栏收窄：隐藏搜索框，压缩按钮与间距，杜绝横向溢出 */
  .topbar { gap: 8px; padding: 0 10px; }
  .topbar .searchbox { display: none; }
  .topbar .brand { font-size: 1rem; flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; }
  .topbar .spacer { display: none; }
  .topbtn { width: 30px; height: 30px; font-size: .76rem; }
  .topbar .burger { width: 32px; }
  main.content { padding: 18px 14px 56px; }
  .hero { padding: 22px 16px 18px; }
  .motto .m-main { font-size: 1.02rem; letter-spacing: 2px; }
  .card { padding: 16px; }
}
@media print {
  .topbar, .sidebar, .pager, details.ans summary, .side-mask { display: none; }
  details.ans { display: block; }
  main.content { max-width: none; }
}