/* Axiom Learning《AP微积分讲义》网页版样式 —— 配色与 axiomhandout.sty 一致 */
:root {
  --navy: #0b336e; --deep: #0a1f45; --blue: #2f6db5; --sky: #edf3fa; --gold: #e3a535;
  --amber: #c47a1b; --cream: #fbf5e8; --paper: #f4f6f9; --gray: #6a7385; --line: #d3d9e3;
  --alert: #c8412f; --ok: #2e8b57; --ink: #1f2430; --bg: #fff;
  --serif: "Songti SC", "STSong", "Noto Serif SC", "Source Han Serif SC", "SimSun", serif;
  --sans: "Avenir Next", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", sans-serif;
  --kai: "Kaiti SC", "STKaiti", "KaiTi", serif;
  --topbar: 52px; --tocw: 250px;
}
* { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--topbar) + 14px); }
body { margin: 0; background: var(--bg); color: var(--ink); font-family: var(--serif);
       font-size: 17px; line-height: 1.8; -webkit-text-size-adjust: 100%; }
a { color: var(--blue); }
b { color: #11182a; }

/* ---------- 顶栏 ---------- */
.topbar { position: fixed; top: 0; left: 0; right: 0; height: var(--topbar); z-index: 20;
  display: flex; align-items: center; gap: 14px; padding: 0 16px;
  background: var(--deep); color: #fff; border-bottom: 3px solid var(--gold); font-family: var(--sans); }
.topbar .brand img { height: 30px; display: block; }
.tb-title { font-size: 15px; font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; flex: 1; min-width: 0; }
.tb-sep { color: var(--gold); margin: 0 8px; }
.teacher { font-size: 13px; color: #c9d3e3; white-space: nowrap; cursor: pointer; user-select: none; }
.teacher input { accent-color: var(--gold); vertical-align: -2px; }
.tocbtn { display: none; background: none; border: 0; color: #fff; font-size: 22px; cursor: pointer; padding: 4px; }

/* ---------- 侧栏目录 ---------- */
.toc { position: fixed; top: var(--topbar); bottom: 0; left: 0; width: var(--tocw); overflow-y: auto;
  padding: 18px 10px 30px 16px; border-right: 1px solid var(--line); background: #fbfcfd;
  font-family: var(--sans); font-size: 14px; line-height: 1.45; z-index: 15; }
.toc-h { color: var(--navy); font-weight: 700; margin: 0 0 10px 6px; }
.toc ol { list-style: none; margin: 0; padding: 0; }
.toc li a { display: flex; gap: 8px; padding: 6px 8px; border-radius: 4px; color: #3a4357; text-decoration: none; }
.toc li a:hover { background: var(--sky); }
.toc li a.active { background: var(--sky); color: var(--navy); font-weight: 600; box-shadow: inset 3px 0 0 var(--gold); }
.toc .tn { color: var(--gray); min-width: 34px; font-variant-numeric: tabular-nums; }
.toc-home { display: block; margin: 16px 8px 0; font-size: 13px; color: var(--gray); text-decoration: none; }

main { margin-left: var(--tocw); padding: calc(var(--topbar) + 8px) 40px 60px; }
main > * , section > * { max-width: 800px; }
section { max-width: none; }

/* ---------- 章首横幅 ---------- */
.banner { background: linear-gradient(120deg, var(--deep), var(--navy)); color: #fff; border-radius: 6px;
  padding: 28px 30px 26px; margin: 18px 0 10px; position: relative; overflow: hidden; font-family: var(--sans); }
.banner::after { content: ""; position: absolute; right: -40px; bottom: -60px; width: 260px; height: 160px;
  border-top: 3px solid var(--gold); border-radius: 50%; transform: rotate(-18deg); opacity: .7; }
.bn-l { color: var(--gold); font-weight: 600; letter-spacing: .12em; font-size: 14px; }
.banner h1 { margin: 6px 0 4px; font-size: 32px; line-height: 1.3; font-weight: 700; }
.bn-en { color: #b9c4d6; font-size: 15px; }

/* ---------- 标题 ---------- */
h2 { font-family: var(--sans); color: var(--navy); font-size: 25px; line-height: 1.35; margin: 54px 0 14px;
  padding-bottom: 8px; border-bottom: 1px solid var(--line); display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 12px; }
h2 .secnum { color: var(--gold); font-weight: 700; }
h2 .en { color: var(--gray); font-size: 15px; font-weight: 500; flex-basis: 100%; }
h3 { font-family: var(--sans); color: var(--navy); font-size: 18px; margin: 28px 0 8px; line-height: 1.45; }
h3::before { content: ""; display: inline-block; width: 3px; height: .95em; background: var(--gold);
  margin-right: 9px; vertical-align: -2px; }
p { margin: .55em 0; }
.dmath { overflow-x: auto; overflow-y: hidden; margin: .5em 0; padding: 2px 0; }
.katex-display { margin: .35em 0; }
.katex { font-size: 1.06em; }
ol, ul { padding-left: 1.6em; }
li { margin: .35em 0; }
li.lbl { list-style: none; }
.li-lbl { margin-left: -1.6em; display: inline-block; width: 1.6em; }
.center { text-align: center; }
.center > p { text-align: left; }
.ding { color: var(--ok); font-weight: 700; }
a.xref { text-decoration: none; border-bottom: 1px dotted var(--blue); }

/* ---------- 表格 ---------- */
.tabwrap { overflow-x: auto; margin: .6em 0; position: relative; }
table.tab { border-collapse: collapse; margin: 0 auto; font-variant-numeric: tabular-nums; }
table.tab td { padding: 4px 14px; vertical-align: middle; }
table.tab td.al-l { text-align: left; } table.tab td.al-c { text-align: center; } table.tab td.al-r { text-align: right; }
table.tab td.bl { border-left: 1px solid #8b93a3; }
table.tab tr.ht td { border-top: 1px solid #8b93a3; }
table.tab td p { margin: 0; }
.cmthm table.tab td { padding: 7px 16px; }   /* 对应 PDF 里的 \arraystretch */
.tabtools { text-align: center; margin: 4px 0 2px; font-family: var(--sans); }
.tabtools button, .chip-btn { font-family: var(--sans); font-size: 13px; background: var(--sky); color: var(--navy);
  border: 1px solid #cbd8ea; border-radius: 14px; padding: 2px 12px; margin: 2px 3px; cursor: pointer; }
.tabtools button.on { background: var(--navy); color: #fff; border-color: var(--navy); }
table.masked td.mask { color: transparent; background: repeating-linear-gradient(45deg, #eef1f6 0 6px, #e4e9f1 6px 12px);
  cursor: pointer; border-radius: 3px; }
table.masked td.mask * { visibility: hidden; }
table.masked td.mask.peek { color: inherit; background: var(--cream); }
table.masked td.mask.peek * { visibility: visible; }

/* ---------- 盒子 ---------- */
.box { margin: 16px 0 18px; padding: 14px 18px 12px; border-radius: 3px; }
.box-h { font-family: var(--sans); font-weight: 700; font-size: 15px; margin-bottom: 4px; display: flex; flex-wrap: wrap; gap: 4px 12px; align-items: baseline; }
.box-t { color: var(--navy); }
.box-b > p:first-child { margin-top: .2em; }
.cmdef { background: var(--sky); border-left: 4px solid var(--navy); }
.cmdef .box-l { color: var(--navy); }
.cmthm { border: 1px solid var(--navy); padding: 0; border-radius: 5px; overflow: hidden; }
.cmthm .box-h { background: var(--navy); color: #fff; padding: 8px 18px; margin: 0; }
.cmthm .box-t { color: #fff; }
.cmthm .box-b { padding: 8px 18px 12px; }
.cmnote { background: var(--cream); border-left: 4px solid var(--gold); }
.cmnote .box-l { color: var(--amber); }
.cmex { background: var(--paper); border-radius: 5px; }
.cmex .box-l, .cmthink .box-l { color: #fff; background: var(--navy); border-radius: 3px; padding: 1px 9px; font-size: 13px; }
.cmthink { border: 1px solid var(--line); border-radius: 5px; }
.cmthink .box-l { background: var(--amber); }

/* ---------- 解答 / 答案折叠 ---------- */
details > summary { cursor: pointer; list-style: none; font-family: var(--sans); user-select: none; }
details > summary::-webkit-details-marker { display: none; }
details.sol { margin-top: 12px; border-top: 1px dashed #aab2c0; padding-top: 8px; }
details.sol > summary { display: inline-flex; align-items: center; gap: 6px; color: var(--amber); font-weight: 700; font-size: 14px;
  padding: 3px 12px 3px 10px; border: 1px solid #ecd3ae; border-radius: 15px; background: #fff; }
details.sol > summary span { font-size: 15px; }
details.sol > summary::before { content: "▸"; transition: transform .15s; }
details.sol[open] > summary::before { transform: rotate(90deg); }
details.sol:not([open]) > summary::after { content: "先自己想，再点开"; color: var(--gray); font-weight: 400; font-size: 12px; margin-left: 6px; }
.sol-body { padding: 4px 0 0; }
details.ans { margin: 4px 0 8px; }
details.ans > summary { display: inline-block; font-size: 12.5px; color: var(--blue); padding: 0 10px; border: 1px solid #cbd8ea;
  border-radius: 12px; background: var(--sky); line-height: 1.8; }
details.ans[open] > summary { background: var(--blue); color: #fff; border-color: var(--blue); }
details.ans > div { margin-top: 6px; padding: 6px 12px; border-left: 3px solid var(--gold); background: #fffdf7; }
details.ans > div p { margin: .2em 0; }
.box-tools { float: right; margin-top: -2px; }

/* 判断题 */
.tf { margin: 4px 0 2px; font-family: var(--sans); font-size: 13px; display: flex; gap: 6px; align-items: center; flex-wrap: wrap; }
.tf button { font: inherit; padding: 1px 14px; border-radius: 12px; border: 1px solid var(--line); background: #fff; cursor: pointer; }
.tf button.right { background: var(--ok); color: #fff; border-color: var(--ok); }
.tf button.wrongpick { background: var(--alert); color: #fff; border-color: var(--alert); }
.tf-msg { color: var(--gray); }

/* 常见错误 */
p.wrong { background: #fdf1ef; border-left: 4px solid var(--alert); padding: 6px 14px; border-radius: 0 3px 3px 0; }
details.fix { margin: 6px 0 14px; }
details.fix > summary { display: inline-block; font-size: 13px; color: var(--ok); border: 1px solid #b9dcc8;
  background: #f1f9f4; border-radius: 14px; padding: 1px 12px; }
details.fix[open] > summary { display: none; }
details.fix > p { background: #f1f9f4; border-left: 4px solid var(--ok); padding: 6px 14px; margin: 0; border-radius: 0 3px 3px 0; }

/* ---------- 图与互动组件 ---------- */
figure.cmfig { margin: 20px 0 22px; padding: 0; }
.widget { border: 1px solid var(--line); border-radius: 6px; background: #fff; min-height: 80px; overflow: hidden; }
.widget-loading, .widget-error { color: var(--gray); font-family: var(--sans); font-size: 14px; text-align: center; padding: 34px 12px; }
.widget-error { background: var(--paper); }
figcaption { font-family: var(--kai); color: var(--gray); font-size: 15px; text-align: center; margin-top: 8px; }
img.fig-static { display: block; margin: 0 auto; max-width: 100%; height: auto; }
span.tab-inner { display: inline-block; }
.fig-missing { border: 1px dashed var(--line); color: var(--gray); text-align: center; padding: 24px; font-family: var(--sans); font-size: 14px; }

footer { margin-top: 70px; padding-top: 14px; border-top: 1px solid var(--line); color: var(--gray); font-size: 13px; font-family: var(--sans); }

/* ---------- 目录页 ---------- */
body.index main.ix { margin: 0 auto; max-width: 820px; padding: 10px 16px 60px; }
.ix-banner { max-width: 820px; margin: 24px auto 10px; }
.ix-banner img { height: 40px; display: block; margin-bottom: 14px; }
@media (max-width: 852px) { .ix-banner { margin: 16px 16px 10px; } }
.ix-list { list-style: none; padding: 0; margin: 18px 0; }
.ix-list li > a, .ix-list li.soon { display: grid; grid-template-columns: 74px 1fr; gap: 0 12px; padding: 14px 16px;
  border: 1px solid var(--line); border-radius: 6px; margin: 10px 0; text-decoration: none; color: var(--ink); font-family: var(--sans); }
.ix-list li > a:hover { border-color: var(--navy); background: var(--sky); }
.ix-n { color: var(--gold); font-weight: 700; grid-row: span 2; align-self: center; }
.ix-t { font-weight: 600; color: var(--navy); }
.ix-en { color: var(--gray); font-size: 13px; }
.ix-list li.soon { opacity: .55; position: relative; }
.ix-soon { position: absolute; right: 14px; top: 14px; font-size: 12px; color: var(--gray); }

/* ---------- 手机 ---------- */
@media (max-width: 960px) {
  .tocbtn { display: block; }
  .toc { transform: translateX(-100%); transition: transform .2s; box-shadow: 4px 0 18px rgba(0,0,0,.12); width: 280px; }
  body.toc-open .toc { transform: none; }
  main { margin-left: 0; padding: calc(var(--topbar) + 4px) 16px 50px; }
  .tb-title { font-size: 14px; }
}
@media (max-width: 560px) {
  body { font-size: 16px; }
  .teacher { font-size: 12px; }
  .topbar { gap: 10px; padding: 0 10px; }
  .topbar .brand { display: none; }
  .banner { padding: 20px 18px; }
  .banner h1 { font-size: 25px; }
  h2 { font-size: 21px; }
  .box { padding: 12px 13px 10px; }
  .cmthm .box-h, .cmthm .box-b { padding-left: 13px; padding-right: 13px; }
  table.tab td { padding: 4px 8px; }
}

/* ---------- 打印 ---------- */
@media print {
  .topbar, .toc, .tabtools, .tf { display: none !important; }
  main { margin: 0; padding: 0; }
  body { font-size: 11pt; }
  .box, figure, table { break-inside: avoid; }
  details > summary { display: none !important; }
  .banner, .cmthm .box-h, .cmex .box-l, .cmthink .box-l { -webkit-print-color-adjust: exact; print-color-adjust: exact; }
}