:root{
  --bg:#f4f6fb; --card:#fff; --ink:#1d2330; --sub:#5d6677; --line:#e3e8f2;
  --brand:#4f46e5; --brand2:#7c6cf0;
  --green:#16a34a; --amber:#d97706; --red:#dc2626;
  --shadow:0 8px 24px rgba(20,30,60,.08);
}
*{box-sizing:border-box;margin:0;padding:0}
body{
  font-family:"PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  background:var(--bg); color:var(--ink); line-height:1.75;
  -webkit-font-smoothing:antialiased;
}
.wrap{max-width:1080px;margin:0 auto;padding:0 20px 80px}

/* 顶部导航 */
.topbar{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.93);
  backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.topbar .inner{max-width:1080px;margin:0 auto;padding:9px 76px 9px 20px;display:flex;align-items:center;gap:14px;flex-wrap:wrap}
.brand{font-weight:800;font-size:17px;color:var(--brand);letter-spacing:1px;text-decoration:none;white-space:nowrap}
.nav{display:flex;gap:4px;flex-wrap:wrap}
.nav a{font-size:13.5px;color:var(--sub);text-decoration:none;padding:5px 12px;border-radius:999px;border:1px solid transparent;transition:.15s}
.nav a:hover{color:var(--brand);background:#eef0ff;border-color:#dfe2ff}
.nav a.on{color:#fff;background:var(--brand);border-color:var(--brand)}

/* 卡片 */
.card{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:22px 24px;box-shadow:var(--shadow);margin:16px 0}
h1{font-size:clamp(24px,4vw,34px);letter-spacing:1px;margin:26px 0 8px}
h2{font-size:20px;margin:8px 0 12px;padding-left:10px;border-left:4px solid var(--brand)}
h3{font-size:16.5px;margin:18px 0 6px;color:#2b3446}
p{margin:8px 0}
.lead{color:var(--sub);font-size:14.5px}
.small{font-size:13px;color:var(--sub)}
hr{border:none;border-top:1px solid var(--line);margin:18px 0}

/* 徽章 */
.badge{display:inline-block;font-size:12px;padding:1px 9px;border-radius:999px;font-weight:600;vertical-align:middle;line-height:1.9}
.b-base{background:#e7f7ec;color:var(--green)}
.b-mid{background:#fef3e2;color:var(--amber)}
.b-hi{background:#fdeaea;color:var(--red)}
.b-tag{background:#eef0ff;color:var(--brand)}

/* 公式 */
.m{font-family:"Times New Roman","STIX Two Math",serif;font-style:italic}
.frac{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;font-size:.86em;margin:0 3px}
.frac .n{border-bottom:1.4px solid currentColor;padding:0 4px;line-height:1.2}
.frac .d{padding:0 4px;line-height:1.2}
.formula{background:#f8f9fd;border:1px solid var(--line);border-radius:10px;padding:12px 16px;margin:10px 0;
  font-family:"Times New Roman",serif;font-size:17px;overflow-x:auto;line-height:2}
.formula b{color:var(--brand)}

/* 表格 */
table{border-collapse:collapse;width:100%;margin:10px 0;font-size:14.5px}
th,td{border:1px solid var(--line);padding:8px 10px;text-align:left;vertical-align:top}
th{background:#f3f5fb;font-weight:600}
tbody tr:nth-child(even){background:#fafbfe}

/* 列表 */
ul,ol{margin:8px 0 8px 22px}
li{margin:4px 0}

/* 折叠 */
details{border:1px solid var(--line);border-radius:12px;padding:10px 16px;margin:10px 0;background:#fbfcff}
summary{cursor:pointer;font-weight:600;color:var(--brand);font-size:14.5px}
details[open] summary{margin-bottom:8px}

/* 题目 */
.q{border:1px solid var(--line);border-radius:14px;padding:16px 18px;margin:14px 0;background:#fff}
.q .qt{font-size:15.5px;margin:8px 0}
.q .opts{display:grid;gap:8px;margin-top:10px}
.opt{border:1px solid var(--line);border-radius:10px;padding:9px 14px;cursor:pointer;font-size:14.5px;
  transition:.15s;background:#fff;text-align:left;font-family:inherit;color:inherit;width:100%}
.opt:hover{border-color:var(--brand);background:#f7f7ff}
.opt.sel{border-color:var(--brand);background:#eef0ff}
.opt.right{border-color:var(--green);background:#e9f9ee;color:#146c33}
.opt.wrong{border-color:var(--red);background:#fdeceb;color:#aa1111}
.opt.dis{pointer-events:none;opacity:.85}
.exp{margin-top:10px;padding:10px 14px;background:#f8f9fd;border-left:3px solid var(--brand);
  border-radius:0 8px 8px 0;font-size:14px;color:#39415a;display:none}
.exp.show{display:block}
.qmeta{font-size:12.5px;color:var(--sub);display:flex;gap:10px;flex-wrap:wrap;align-items:center}

/* 按钮 */
.btn{display:inline-block;border:none;border-radius:999px;padding:10px 22px;font-size:14.5px;font-weight:600;
  cursor:pointer;background:linear-gradient(90deg,var(--brand),var(--brand2));color:#fff;transition:.2s;font-family:inherit}
.btn:hover{transform:translateY(-2px);box-shadow:0 8px 20px rgba(79,70,229,.3)}
.btn.ghost{background:#fff;color:var(--brand);border:1px solid #dfe2ff}
.btn:disabled{opacity:.5;cursor:not-allowed;transform:none;box-shadow:none}

/* 进度条 */
.bar{height:8px;border-radius:999px;background:#e8ebf5;overflow:hidden;margin:6px 0}
.bar > i{display:block;height:100%;background:linear-gradient(90deg,var(--brand),var(--brand2));width:0;transition:.3s}

/* 首页网格 */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:14px;margin-top:14px}
.gcard{display:block;background:#fff;border:1px solid var(--line);border-radius:16px;padding:20px;
  text-decoration:none;color:var(--ink);box-shadow:var(--shadow);transition:.2s}
.gcard:hover{transform:translateY(-4px);border-color:#c9cdff}
.gcard .ico{font-size:26px}
.gcard b{display:block;margin:8px 0 4px;font-size:16px}
.gcard span{font-size:13px;color:var(--sub)}

/* 步骤/路径 */
.steps{counter-reset:s;margin:14px 0 0;padding:0;list-style:none}
.steps li{counter-increment:s;position:relative;padding:12px 16px 12px 52px;margin:10px 0;
  background:#fff;border:1px solid var(--line);border-radius:12px;box-shadow:var(--shadow)}
.steps li::before{content:counter(s);position:absolute;left:14px;top:12px;width:26px;height:26px;
  border-radius:50%;background:var(--brand);color:#fff;font-size:13px;font-weight:700;
  display:flex;align-items:center;justify-content:center}

@media print{.topbar,.btn{display:none}body{background:#fff}.card{box-shadow:none}}
@media(max-width:560px){.card{padding:16px}.wrap{padding:0 14px 60px}.nav a{padding:4px 9px;font-size:12.5px}}

/* ================= 精讲 · 随堂测（learn.js） ================= */
.lqbox{margin:6px 0}
.lq{border:1px solid var(--line);border-radius:14px;padding:16px 18px;margin:14px 0;background:#fff;box-shadow:0 2px 10px rgba(20,30,60,.04)}
.lq-q{font-size:15.5px;margin:10px 0 2px;line-height:1.8}
.lq-opts{display:grid;gap:8px;margin-top:10px}
.lq-opt{display:flex;gap:10px;align-items:flex-start;border:1px solid var(--line);border-radius:10px;
  padding:9px 14px;cursor:pointer;font-size:14.5px;transition:.15s;background:#fff;text-align:left;
  font-family:inherit;color:inherit;width:100%;line-height:1.7}
.lq-opt:hover{border-color:var(--brand);background:#f7f7ff}
.lq-opt .lq-l{flex:0 0 22px;font-weight:800;color:var(--brand);text-align:center}
.lq-opt.right{border-color:var(--green);background:#e9f9ee;color:#146c33}
.lq-opt.right .lq-l{color:var(--green)}
.lq-opt.wrong{border-color:var(--red);background:#fdeceb;color:#aa1111}
.lq-opt.wrong .lq-l{color:var(--red)}
.lq-opt.dis{pointer-events:none;opacity:.92}

.lq-fb{display:none}
.lq-fb.show{display:block;margin-top:12px;padding:12px 14px;border-radius:10px;font-size:14px;line-height:1.8}
.lq-fb.bad{background:#fff5f5;border-left:4px solid var(--red)}
.lq-fb.ok{background:#f2fbf5;border-left:4px solid var(--green)}
.fb-exp{margin-top:6px;color:#39415a}
.fb-tip{margin-top:8px;font-size:13px;color:var(--sub)}

.lq-tools{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}
.btn2{border:1px dashed #cfd6ea;background:#fbfcff;color:#4a5570;border-radius:999px;
  padding:6px 14px;font-size:13px;cursor:pointer;font-family:inherit;transition:.15s;font-weight:600}
.btn2:hover{background:#eef0ff;border-color:var(--brand);color:var(--brand)}
.btn2.kp:hover{background:#fff8e8;border-color:#e0a020;color:#a86b00}

.lq-hint{margin-top:10px}
.lq-hint:not(:empty){background:#fffaf0;border-left:4px solid #e0a020;border-radius:0 8px 8px 0;padding:10px 14px;font-size:14px}
.lq-ansbox{margin-top:10px}
.lq-ansbox:not(:empty){background:#f4f7ff;border-left:4px solid var(--brand);border-radius:0 8px 8px 0;padding:10px 14px;font-size:14px}
.ans-line{color:#146c33;margin-bottom:4px}
.ans-exp{color:#39415a}

.lqscore{margin:10px 0 4px;padding:10px 14px;border-radius:10px;background:#f2f4fb;border:1px solid var(--line);
  font-size:13.5px;color:#39415a}
.lqscore .lq-num{color:var(--brand);font-size:16px}

/* 每个知识点小节的编号 */
.lsec{display:flex;gap:10px;align-items:center;margin:26px 0 8px}
.lsec .no{flex:0 0 34px;height:34px;border-radius:10px;background:linear-gradient(135deg,var(--brand),var(--brand2));
  color:#fff;font-weight:800;display:flex;align-items:center;justify-content:center;font-size:15px}
.lsec h2{border:none;padding:0;margin:0;font-size:20px}

/* 返回按钮 */
.backtop{position:fixed;right:18px;bottom:18px;z-index:60;background:var(--brand);color:#fff;
  text-decoration:none;padding:9px 16px;border-radius:999px;font-size:13px;font-weight:700;
  box-shadow:0 8px 22px rgba(79,70,229,.35);opacity:.92}
.backtop:hover{opacity:1}
.backtop.back2{bottom:64px;background:#fff;color:var(--brand);border:1px solid #dfe2ff;box-shadow:0 6px 18px rgba(20,30,60,.12)}
@media print{.backtop{display:none}}

/* 符号对照表 */
.sym{display:grid;grid-template-columns:64px 1fr;gap:6px 12px;margin:10px 0;font-size:14.5px}
.sym b{font-family:"Times New Roman",serif;font-style:italic;color:var(--brand);font-size:16px}

/* 图像卡片 */
.gwrap{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:14px;margin:12px 0}
.gcard2{border:1px solid var(--line);border-radius:12px;padding:10px;background:#fff;text-align:center}
.gcard2 svg{display:block;margin:0 auto;max-width:100%;height:auto}
.gcard2 .cap{font-size:13px;color:var(--sub);margin-top:6px}

/* 可背诵篇目 */
.recite{background:#fffef8;border:1px solid #efe6c8;border-radius:12px;padding:14px 18px;margin:12px 0;font-size:14.5px;line-height:2}
.recite .title{font-weight:800;color:#8a6a10;font-size:15.5px;margin-bottom:6px}
.recite .src{font-size:12.5px;color:var(--sub);font-weight:400}

/* 二级导航（科目内的页面切换） */
.subnav{background:#f7f8fd;border-bottom:1px solid var(--line)}
.subnav .inner2{max-width:1080px;margin:0 auto;padding:8px 20px;display:flex;gap:6px;flex-wrap:wrap;align-items:center}
.subnav .lab{font-size:12.5px;color:var(--sub);font-weight:700;margin-right:2px}
.subnav a{font-size:13px;color:#4a5570;text-decoration:none;padding:4px 11px;border-radius:8px;
  border:1px solid var(--line);background:#fff;transition:.15s}
.subnav a:hover{color:var(--brand);border-color:#dfe2ff;background:#eef0ff}
.subnav a.on{color:#fff;background:var(--brand);border-color:var(--brand);font-weight:700}

/* 右上角头像 */
.avatarDock{position:fixed;top:12px;right:16px;z-index:70}
.avBtn{position:relative;width:44px;height:44px;border-radius:50%;border:2px solid #fff;
  background:linear-gradient(135deg,var(--brand),var(--brand2));cursor:pointer;padding:0;
  display:flex;align-items:center;justify-content:center;overflow:hidden;
  box-shadow:0 6px 18px rgba(30,40,80,.28);transition:.18s}
.avBtn:hover{transform:translateY(-2px) scale(1.04);box-shadow:0 10px 24px rgba(30,40,80,.34)}
.avImg{width:100%;height:100%;object-fit:cover;display:block}
.avGuest{font-size:21px;line-height:1}
.avDot{position:absolute;right:0;bottom:0;width:12px;height:12px;border-radius:50%;border:2px solid #fff}
.avDot.ok{background:#16a34a}
.avDot.guest{background:#f59e0b}

/* 头像弹窗 */
.avMask{position:fixed;inset:0;background:rgba(18,24,40,.42);backdrop-filter:blur(3px);
  z-index:200;display:none;align-items:center;justify-content:center;padding:20px}
.avMask.on{display:flex}
.avPop{background:#fff;border-radius:20px;padding:26px 24px;max-width:360px;width:100%;
  box-shadow:0 24px 60px rgba(20,30,60,.3);animation:avIn .18s ease-out}
@keyframes avIn{from{transform:translateY(10px) scale(.97);opacity:0}to{transform:none;opacity:1}}
.avPop h3{font-size:18px;margin-bottom:10px;border:none;padding:0}
.avNote{font-size:14px;color:#4a5570;line-height:1.9;margin:0}
.avActs{display:flex;gap:10px;margin-top:20px;justify-content:flex-end;flex-wrap:wrap}
.avActs .btn,.avActs .btn.ghost{padding:9px 18px;font-size:13.5px;text-decoration:none}
@media(max-width:560px){.avatarDock{top:8px;right:10px}.avBtn{width:38px;height:38px}}
@media print{.avatarDock,.avMask{display:none}}

/* 每个知识点后面的随堂测盒子 */
.kpqwrap{margin:16px 0 22px;padding:14px 16px 16px;background:#f7f8ff;border:1px solid #e0e5f4;border-radius:14px}
.kplab{font-size:13px;font-weight:800;color:var(--brand);margin-bottom:8px;letter-spacing:.4px}
.kpqwrap .lq{background:#fff;box-shadow:none;margin:11px 0}
.kpqwrap .lqscore{margin:4px 0 6px;background:#eef0fb;border-color:#dde2f3}
/* 水印「伊蕾娜喵」 */
.elainaWm{position:fixed;top:-40%;left:-40%;width:180%;height:180%;z-index:-1;pointer-events:none;
  display:grid;grid-template-columns:repeat(7,1fr);gap:56px 34px;transform:rotate(-22deg);
  opacity:.075;user-select:none}
.elainaWm span{font-size:17px;font-weight:800;color:#4f46e5;white-space:nowrap;text-align:center;
  letter-spacing:3px;font-family:"PingFang SC","Microsoft YaHei",sans-serif}
@media print{.elainaWm{display:none}}

/* 重做按钮 */
.resetbtn{border:1px dashed #c9cfe4;background:#fff;color:#4a5570;border-radius:999px;
  padding:3px 12px;font-size:12px;cursor:pointer;font-family:inherit;font-weight:700;margin-left:8px}
.resetbtn:hover{border-color:var(--brand);color:var(--brand);background:#eef0ff}