/* 专题知识课 · 入口页与讲义页样式（叠加在共享外壳 chapter.css 之上；入口页单独使用）
   配色、字体、Logo 与「高中数学教册-谭老师html-1.0」一致。 */
:root{--bg:#f4f5f1;--paper:#fff;--ink:#17343c;--muted:#667b80;--line:#dce5e1;--soft:#eef3ef;--teal:#22786f;--teal-d:#1b655d;--teal2:#40a79b;--navy:#213d52;--gold:#b28036;--purple:#7a5ea8;--red:#b9573f;--green:#3b8a5c;
  --mono:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;--sans:-apple-system,BlinkMacSystemFont,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;--kai:"Kaiti SC","STKaiti","KaiTi","BiauKai",serif;
  --col:980px}
*{box-sizing:border-box}

/* ---------- 统一 Logo：谭老师的数学课 ---------- */
.tlogo{display:block;flex:none}
.kc-home,.logo{display:flex;align-items:center;gap:11px;color:var(--ink);text-decoration:none}
.kc-home:hover,.logo:hover{text-decoration:none}
.kc-home span,.logo span{display:block;min-width:0}
.kc-home b,.logo b{display:block;font-weight:760;letter-spacing:.1em;line-height:1.3;white-space:nowrap}
.kc-home small,.logo small{display:block;font:10.5px/1.5 var(--mono);letter-spacing:.12em;color:var(--muted);white-space:nowrap}

/* ---------- 入口页（index.html） ---------- */
body.library{margin:0;min-height:100vh;background:var(--bg);font-family:var(--sans);color:var(--ink)}
.library-head{background:#fbfcfa;border-bottom:1px solid var(--line);padding:25px max(24px,calc((100vw - 1120px)/2)) 32px}
.library-head .kc-home .tlogo{width:40px;height:40px}.library-head .kc-home b{font-size:16px}
.library-head .eyebrow{margin:34px 0 6px;font:11px var(--mono);letter-spacing:.16em;color:var(--teal)}
.library-head h1{font-size:34px;line-height:1.2;margin:0}
.library-grid{max-width:1120px;margin:auto;padding:34px 24px 50px;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}
.book{position:relative;background:#fff;border:1px solid var(--line);border-left:4px solid var(--teal);border-radius:10px;padding:20px 24px;color:inherit;text-decoration:none;min-height:118px;transition:border-color .15s,box-shadow .15s}
.book:hover{border-color:var(--teal);box-shadow:0 8px 22px #17343c12}
.book-no{font:11px var(--mono);color:var(--teal)}
.book h2{font-size:19px;line-height:1.4;margin:7px 28px 8px 0}
.book p{font-size:12.5px;color:var(--muted);margin:0}
.book-arrow{position:absolute;right:22px;top:22px;color:var(--teal)}
.library footer{text-align:center;color:var(--muted);font-size:12px;padding:0 20px 30px}
@media(max-width:760px){.library-grid{grid-template-columns:1fr}.library-head h1{font-size:27px}}

/* =====================================================================
   讲义页（book-0N.html）
   ===================================================================== */
body.topic-book{font-size:17px;line-height:1.9;background:var(--bg)}
html{scroll-padding-top:20px}

/* ---------- 正文栏：居中的阅读宽度 ---------- */
body.topic-book main.kc-main{max-width:none;padding:44px clamp(24px,4.5vw,72px) 110px}
main.kc-main>section{max-width:var(--col);margin-left:auto;margin-right:auto}
body.topic-book section.lesson{margin-top:72px;padding-top:8px;border-top:3px solid var(--line)}

/* ---------- 专题页眉 ---------- */
body.topic-book .lesson-head{padding:16px 0 22px;margin-bottom:6px}
body.topic-book .lesson-head .no{color:var(--teal);font-weight:650;letter-spacing:.12em}
body.topic-book .lesson-head h2{font-size:clamp(25px,2.6vw,32px);line-height:1.38;margin:6px 0 10px;overflow-wrap:anywhere}
.lesson-head .lead{font-family:var(--kai);font-size:18.5px;color:#58716f;margin:0 0 4px}
.open-demo{margin-top:14px;background:var(--teal);color:#fff;border-color:var(--teal);font-size:14px;font-weight:650;padding:7px 16px;border-radius:9px}
.open-demo:hover{background:var(--teal-d);color:#fff}

/* ---------- 正文层级 ---------- */
.unit{overflow-wrap:break-word}
body.topic-book article.unit{margin-top:8px}
.unit>p,.unit li,.unit .box p{max-width:100%}
.unit h2{font-size:24px;line-height:1.45;margin:46px 0 14px;padding-left:14px;border-left:4px solid var(--teal);color:var(--ink)}
.unit h3,article.unit>h3{font-size:20px;border:0;padding:0;line-height:1.5;margin:32px 0 10px;color:var(--navy);border:0;padding:0}
.unit h3::before{content:"";display:inline-block;width:7px;height:7px;border-radius:2px;background:var(--teal2);margin-right:10px;vertical-align:4px}
.unit h4{font-size:17.5px;margin:24px 0 8px;color:#2c4f57}
.unit h5{font-size:16px;margin:18px 0 6px;color:#3a5a60}
.unit strong{color:#0f2c33}
.unit a{text-decoration:underline;text-decoration-color:#22786f55;text-underline-offset:3px}
.unit hr{border:0;border-top:1px dashed var(--line);margin:28px 0}
.unit>blockquote,.unit .box blockquote{margin:16px 0;padding:6px 18px;border-left:3px solid var(--teal2);background:#eef5f1;border-radius:0 10px 10px 0;color:#476662}
.unit blockquote p{margin:6px 0}
/* 推导步骤：编号 + 每步理由（列表项里的 > ） */
.unit ol{padding-left:1.9em}
.unit ol>li::marker{color:var(--purple);font-weight:700;font-family:var(--mono);font-size:.9em}
.unit ul>li::marker{color:var(--teal2)}
.unit li{margin:6px 0}
.unit li>blockquote{margin:2px 0 6px;padding:0 0 0 1.4em;border:0;background:none;font-family:var(--kai);font-size:.94em;color:#6c7f80;position:relative}
.unit li>blockquote::before{content:"";position:absolute;left:0;top:.95em;width:.9em;border-top:1px solid #a9b8b6}
.unit p>em:only-child{display:block;text-align:center;font-style:normal;color:var(--teal2)}
.lv{display:inline-block;font-size:12px;font-weight:650;line-height:1.6;letter-spacing:.04em;border-radius:5px;padding:0 7px;margin:0 6px 0 2px;vertical-align:2px;background:#ece5f6;color:#5f4790;border:1px solid #d9cdec;font-family:var(--sans)}
.lv-top{background:#f8e3dc;color:#97462f;border-color:#ecc6b9}
.lv-ext,.lv-opt{background:#e6eef7;color:#2e5a8e;border-color:#c9d8ea}
.lv-base{background:#e1f0eb;color:#176b60;border-color:#c3e0d6}

/* ---------- 提示框（与讲义「版式约定」一致） ---------- */
.unit .box{border:1px solid var(--line);border-left:4px solid var(--c);background:var(--bgc);border-radius:12px;padding:12px 20px 10px;margin:20px 0}
.unit .box>.tag{display:inline-block;font-size:12.5px;font-weight:700;letter-spacing:.05em;border-radius:6px;padding:1px 10px;margin:2px 0 2px;background:var(--tagbg);color:var(--c)}
.unit .box>p:first-of-type{margin-top:6px}
.unit .box>:last-child{margin-bottom:6px}
.box-idea{--c:#6a4f9a;--bgc:#f8f5fc;--tagbg:#ebe3f6}
.box-warn{--c:#8a6526;--bgc:#fff8ea;--tagbg:#f6e7c8}
.box-bad{--c:#a3482f;--bgc:#fdf3f0;--tagbg:#f6dfd7}
.box-good{--c:#2f7350;--bgc:#f1f9f4;--tagbg:#d8eee1}
.box-note{--c:#4f6468;--bgc:#f5f7f6;--tagbg:#e4eaE8}
.unit .box.box-card{--c:#6a4f9a;background:#fff;border:1.5px solid #b9a5da;border-left-width:1.5px;padding:0 20px 8px;overflow:hidden}
.unit .box.box-card>.tag{display:block;margin:0 -20px 4px;border-radius:0;padding:6px 20px;background:#f3eefa;border-bottom:1px solid #e3d9f1;font-size:13px}

/* ---------- 插图 ---------- */
.fig{margin:24px auto;text-align:center}
.fig img{display:block;margin:0 auto;width:min(100%,calc(var(--fw) * 940px),var(--nw),calc(66vh * var(--ar)));height:auto;background:#fff;border:1px solid #e3eae6;border-radius:12px;cursor:zoom-in;box-shadow:0 1px 3px #17343c0a}
.fig figcaption{max-width:760px;margin:10px auto 0;font-size:14.5px;line-height:1.75;color:#55706f}
.fig-no{display:inline-block;font:600 11px/1.9 var(--mono);color:var(--teal);border:1px solid #cfe1da;border-radius:6px;padding:0 7px;margin-right:8px;vertical-align:1px;background:#fff}
.fig-legend{display:block;margin-top:4px;font-size:13px;color:#7c8f90}
.fig-legend.solo{text-align:center;margin:-10px 0 22px}
.fig-row{display:grid;grid-template-columns:repeat(var(--n),minmax(0,1fr));gap:18px;align-items:end;margin:24px 0}
.fig-row .fig{margin:0}
.fig-row .fig img{width:min(100%,var(--nw),calc(56vh * var(--ar)))}
li .fig img{width:min(100%,calc(var(--fw) * 860px),var(--nw),calc(60vh * var(--ar)))}

/* ---------- 表格与长公式 ---------- */
.table-wrap{overflow-x:auto;margin:18px 0;border:1px solid var(--line);border-radius:12px;background:#fff;scrollbar-width:thin}
.table-wrap table{border-collapse:collapse;min-width:100%;font-size:15.5px;line-height:1.7}
.table-wrap th{background:#eef4f1;color:#3c5a58;font-weight:650;padding:9px 14px;border-bottom:1px solid #d9e5df;text-align:center;white-space:nowrap}
.table-wrap td{padding:9px 14px;border-top:1px solid #edf1ee;text-align:center;vertical-align:middle;min-width:4.5em}
.table-wrap th+th,.table-wrap td+td{border-left:1px solid #edf1ee}
.table-wrap tbody tr:nth-child(even) td{background:#fafcfb}
.unit .katex{font-size:1.06em;position:relative}
.unit .katex-display{overflow-x:auto;overflow-y:hidden;margin:14px 0;padding:6px 2px;scrollbar-width:thin}
.unit .katex-display>.katex{font-size:1.12em}
.unit .katex.kx-wide{display:inline-block;max-width:100%;overflow-x:auto;overflow-y:hidden;vertical-align:middle;padding-bottom:3px;scrollbar-width:thin}

/* ---------- 例题：题干 + 分步解答 ---------- */
.unit .example{background:#fff;border:1px solid #d3e1db;border-radius:14px;margin:30px 0;overflow:hidden;box-shadow:0 2px 8px #17343c08}
.example .ex-head{display:flex;flex-wrap:wrap;gap:4px 12px;align-items:center;padding:11px 22px;background:#f2f7f4;border-bottom:1px solid #e1ebe6}
.ex-no{font-weight:760;color:#fff;background:var(--teal);border-radius:7px;padding:1px 11px;font-size:15px;white-space:nowrap}
.ex-no .lv{background:#fff3;color:#fff;border-color:#fff6}
.ex-src{font-family:var(--kai);font-size:16px;color:#3c5a58}
.ex-head .ex-src:first-child{font-family:var(--sans);font-size:15px;font-weight:650;color:var(--navy)}
.example .ex-q{padding:12px 24px 8px}
.example .ex-q>.box{margin:12px 0}
.sol{border-top:1px dashed #cfdcd6}
.example.solo .sol{border-top:0}
.sol-bar{display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;padding:10px 24px;background:#fbfcfa}
.sol-tag{font-weight:760;color:var(--teal);font-size:15px}
.sol-count{font:12px var(--mono);color:#8a9c97}
.sol-tools{margin-left:auto;display:flex;flex-wrap:wrap;gap:6px}
.sol-tools button{font-size:13.5px;padding:5px 14px}
.sol-body{padding:4px 24px 16px;border-top:1px solid #edf2ef}
.sol.is-closed .sol-body{display:none}
.sol.is-closed .sol-bar{background:#fbfcfa}
.step-hidden{display:none!important}
.step-new{animation:kc-in .35s ease}
@keyframes kc-in{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}
.sol-body>ol{list-style:none;counter-reset:st;padding:0;margin:10px 0}
.sol-body>ol>li{counter-increment:st;position:relative;padding:8px 4px 8px 44px;margin:0;border-top:1px dashed #e3ebe7}
.sol-body>ol>li:first-child{border-top:0}
.sol-body>ol>li::before{content:counter(st);position:absolute;left:4px;top:11px;width:26px;height:26px;border-radius:50%;background:#e8e1f4;color:#5f4790;font:700 12.5px/26px var(--mono);text-align:center}
.sol-body>ol[start]>li::before{content:counter(st)}
.sol-body h4{font-size:16.5px;margin:16px 0 4px;color:var(--purple)}

/* ---------- 课堂小测 ---------- */
.unit .quiz{background:#fff;border:1px solid #e6dcc6;border-left:4px solid var(--gold);border-radius:14px;padding:14px 22px 16px;margin:24px 0}
.quiz-head .tag{display:inline-block;font-size:12.5px;font-weight:700;letter-spacing:.05em;border-radius:6px;padding:1px 10px;background:#f6e7c8;color:#80612b}
.quiz-stem>p{margin:8px 0}
.unit .quiz-opts{list-style:none;padding:0;margin:10px 0 0;display:grid;grid-template-columns:repeat(var(--c,1),minmax(0,1fr));gap:8px}
.quiz-opts[data-cols="4"]{--c:4}.quiz-opts[data-cols="3"]{--c:3}.quiz-opts[data-cols="2"]{--c:2}
.quiz-opts li{margin:0}
.quiz .opt{width:100%;height:100%;display:flex;gap:10px;align-items:baseline;text-align:left;padding:8px 14px;border:1px solid #d6e2dc;border-radius:10px;background:#fbfcfa;color:var(--ink);font-size:16px;line-height:1.7}
.quiz .opt b{color:var(--teal);font-family:var(--mono);flex:none}
.quiz .opt:hover{border-color:var(--teal2);background:#f1f8f5}
.quiz .opt.right{border-color:#3b9783;background:#e3f3ec;box-shadow:inset 0 0 0 1px #3b9783}
.quiz .opt.wrong{border-color:#d08a74;background:#fbede8;animation:kc-shake .3s}
@keyframes kc-shake{25%{transform:translateX(-3px)}75%{transform:translateX(3px)}}
.quiz-fb{margin:8px 0 0;font-size:14px;color:#55706f;min-height:0}
.quiz-fb:empty{display:none}
.quiz-ans{margin-top:12px}
.quiz-ans>summary{display:inline-flex;align-items:center;gap:6px;cursor:pointer;list-style:none;font-size:13.5px;color:var(--teal);border:1px solid #cfe1da;border-radius:8px;padding:3px 12px;background:#fff}
.quiz-ans>summary::-webkit-details-marker{display:none}
.quiz-ans>summary::before{content:"";width:0;height:0;border:4.5px solid transparent;border-left:6px solid currentColor;border-right:0;transition:transform .15s}
.quiz-ans[open]>summary{background:#e6f1eb}
.quiz-ans[open]>summary::before{transform:rotate(90deg)}
.quiz-ans-body{margin-top:10px;background:#f7faf8;border-radius:10px;padding:10px 18px}
.ans-key{display:flex;gap:10px;align-items:baseline;margin:6px 0}
.ans-key>span{font-weight:700;color:var(--teal);font-size:17px}
.ans-key>b,.ans-part>b{display:inline-block;flex:none;font-size:12px;font-weight:700;border-radius:5px;padding:0 8px;line-height:1.9;background:#e1efe9;color:#176b60}
.ans-part{margin:8px 0}
.ans-part>b{margin-bottom:2px}
.ans-part p{margin:4px 0}
.ans-part ul{margin:4px 0;padding-left:1.3em}

/* ---------- 交互动图弹窗：接近全屏，画板一屏可见 ---------- */
#demo-dialog{width:calc(100vw - 32px);height:calc(100vh - 32px);max-width:1680px;max-height:none;border:0;border-radius:14px;padding:0;background:#f4f5f1;box-shadow:0 24px 80px #0f222866;overflow:hidden}
#demo-dialog[open]{display:flex;flex-direction:column}
#demo-dialog::backdrop{background:#10252bd9}
body.demo-open{overflow:hidden}
.demo-bar{flex:none;height:52px;display:flex;align-items:center;gap:12px;padding:0 12px 0 20px;background:#fbfcfa;border-bottom:1px solid var(--line);font-size:14px}
#demo-title{min-width:0;flex:1;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.demo-bar a{font-size:13px;flex:none}
#demo-close{width:38px;height:38px;padding:0;font-size:24px;line-height:1;flex:none}
#demo-frame{flex:1;min-height:0;width:100%;border:0;background:#f4f5f1}

/* ---------- 手机 ---------- */
@media (max-width:980px){body.topic-book main.kc-main{padding:28px 20px 100px}}
@media (max-width:640px){
  body.topic-book{font-size:16.5px;line-height:1.85}
  body.topic-book main.kc-main{padding:24px 14px 100px}
  .lesson-head .lead{font-size:17px}
  .unit h2{font-size:21px;margin-top:38px}.unit h3{font-size:18.5px}
  .unit .box{padding:10px 14px 8px;border-radius:10px}
  .unit .box.box-card{padding:0 14px 6px}.unit .box.box-card>.tag{margin:0 -14px 4px;padding:6px 14px}
  .example .ex-head{padding:10px 14px}.example .ex-q{padding:10px 14px 6px}
  .sol-bar{padding:10px 14px}.sol-body{padding:4px 14px 14px}.sol-tools{margin-left:0;width:100%}
  .sol-body>ol>li{padding-left:36px}.sol-body>ol>li::before{left:0}
  .unit .quiz{padding:12px 14px 14px}
  .quiz-opts[data-cols="4"]{--c:2}.quiz-opts[data-cols="3"],.quiz-opts[data-cols="2"]{--c:1}
  .unit ol{padding-left:1.5em}
  .fig-row{grid-template-columns:1fr}
  .fig img{width:min(100%,var(--nw),calc(70vh * var(--ar)))}
  .fig figcaption{font-size:13.5px}
  .table-wrap table{font-size:14.5px}.table-wrap th,.table-wrap td{padding:7px 10px}
  #demo-dialog{width:100vw;height:100vh;height:100dvh;max-width:none;border-radius:0;margin:0}
  .demo-bar{padding:0 8px 0 14px}
}

/* ---------- 宽屏 / 投影 ---------- */
@media (min-width:1600px){body.topic-book{font-size:18px}:root{--col:1040px}}

/* ---------- 打印 ---------- */
@media print{
  body.topic-book{font-size:11.5pt;background:#fff}
  .open-demo,.sol-tools,.sol-count,.quiz-fb,.quiz-ans>summary,#demo-dialog{display:none!important}
  body.topic-book main.kc-main{margin:0;padding:0}
  main.kc-main>section{max-width:none}
  body.topic-book section.lesson{break-before:page;border:0;margin:0}
  .sol.is-closed .sol-body{display:block}
  .step-hidden{display:revert!important}
  .quiz-ans>.quiz-ans-body{display:block}
  .fig img{width:min(100%,calc(var(--fw) * 16cm));box-shadow:none}
  .fig,.box,.quiz,.table-wrap,.sol-body>ol>li{break-inside:avoid}
  .unit .example{box-shadow:none}
}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}