/* ============================================================
   凤凰机器人来宾校区课件系统 · 主样式
   ============================================================ */
:root{
  --ink:#1f2a44; --ink-soft:#46536f; --muted:#7a86a5;
  --blue:#3b6fe0; --blue-d:#2c55b0; --purple:#6a4fe0;
  --accent:#ff8f2b; --accent-d:#e07313;
  --green:#2fbf71; --red:#e5533d; --gold:#c9a24b;
  --bg:#f2f6ff; --card:#ffffff; --line:#dde6f7;
  --shadow:0 4px 14px rgba(31,42,68,.06);
  --shadow-lg:0 10px 30px rgba(31,42,68,.12);
  --grad-hero:linear-gradient(135deg,#2c55b0 0%,#3b6fe0 55%,#6a4fe0 100%);
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  font-family:"PingFang SC","Microsoft YaHei","Segoe UI",sans-serif;
  background:var(--bg); color:var(--ink); line-height:1.7;
}
a{text-decoration:none;color:inherit}
button{font-family:inherit}
.lesson{scroll-margin-top:96px}

/* ============ 顶栏 ============ */
.topbar{
  position:sticky;top:0;z-index:50;background:#ffffffee;backdrop-filter:blur(8px);
  border-bottom:2px solid var(--line);
  display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap;
  padding:10px 22px;
}
.brand{display:flex;align-items:center;gap:12px}
.brand-logo{width:44px;height:44px;border-radius:12px;object-fit:cover;box-shadow:0 3px 8px rgba(59,111,224,.25)}
.back-btn{
  font-weight:800;font-size:14.5px;color:var(--blue-d);
  border:2px solid var(--line);border-radius:999px;padding:7px 16px;transition:.2s;background:#fff;
}
.back-btn:hover{border-color:var(--blue);color:var(--blue)}
.brand-title{font-size:17px;font-weight:800}
.brand-sub{font-size:12px;color:var(--muted);letter-spacing:.5px}
.topbar-right{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.role-chip{font-size:12px;font-weight:800;border-radius:999px;padding:4px 12px}
.role-vip{background:#fdf6e3;color:#9a6f14;border:1.5px solid #ecd9a0}
.role-guest{background:#eef2fb;color:#5b6b80;border:1.5px solid var(--line)}
.user-chip{
  display:flex;align-items:center;gap:8px;font-weight:700;font-size:14px;
  background:#fff;border:2px solid var(--line);border-radius:999px;padding:4px 14px 4px 5px;
}
.user-chip img{width:32px;height:32px;border-radius:50%;object-fit:cover}
.logout-btn{font-size:13px;font-weight:700;color:var(--muted);padding:6px 10px;border-radius:8px}
.logout-btn:hover{color:var(--red);background:#fdeeec}

/* ============ 欢迎横幅 ============ */
.hero{background:var(--grad-hero);color:#fff;position:relative;overflow:hidden}
.hero::before{
  content:'';position:absolute;inset:0;
  background:
    radial-gradient(circle at 85% 20%, rgba(255,255,255,.14) 0 120px, transparent 121px),
    radial-gradient(circle at 10% 85%, rgba(255,255,255,.10) 0 90px, transparent 91px);
}
.hero-inner{max-width:1100px;margin:0 auto;padding:52px 20px 44px;position:relative}
.hero-tag{
  display:inline-block;background:#ffffff1f;border:1px solid #ffffff4d;border-radius:999px;
  padding:5px 16px;font-size:12.5px;letter-spacing:2px;font-weight:700;margin-bottom:16px;
}
.hero h1{font-size:clamp(24px,4vw,38px);line-height:1.35;margin-bottom:10px}
.hero p{max-width:780px;font-size:16px;opacity:.94;margin-bottom:22px}
.hero-stats{display:flex;gap:14px;flex-wrap:wrap;margin-bottom:22px}
.stat{
  background:#ffffff17;border:1px solid #ffffff36;border-radius:16px;
  padding:12px 26px;text-align:center;min-width:110px;backdrop-filter:blur(4px);
}
.stat b{display:block;font-size:26px;font-weight:900}
.stat span{font-size:12.5px;opacity:.85}
.hero-chips{display:flex;gap:10px;flex-wrap:wrap}
.chip{background:#ffffff1f;border:1px solid #ffffff4d;border-radius:999px;padding:5px 14px;font-size:13px}
.guest-banner{
  margin-top:20px;background:#ffffff14;border:1.5px dashed #ffffff66;border-radius:12px;
  padding:10px 16px;font-size:14px;display:inline-block;
}
.btn{
  border:none;border-radius:12px;padding:10px 20px;font-size:15px;font-weight:800;cursor:pointer;
  transition:.15s;background:#e9eefb;color:var(--ink);
}
.btn:hover{transform:translateY(-1px)}
.btn:disabled{opacity:.4;cursor:not-allowed;transform:none}
.btn-primary{background:var(--blue);color:#fff}
.btn-ghost{background:#fff;border:2px solid var(--line)}
.btn-warn{background:#ffece8;color:var(--red)}

/* ============ 课程大厅 ============ */
.hall{max-width:1100px;margin:0 auto;padding:34px 20px 10px}
.subject-tabs{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:26px}
.stab{
  border:2px solid var(--line);background:#fff;color:var(--ink);
  padding:9px 18px;border-radius:999px;font-size:14.5px;font-weight:700;cursor:pointer;transition:.2s;
}
.stab em{font-style:normal;font-size:12px;color:var(--muted);margin-left:4px}
.stab:hover{border-color:var(--blue);color:var(--blue)}
.stab.active{background:var(--grad-hero);border-color:transparent;color:#fff;box-shadow:0 4px 12px rgba(59,111,224,.3)}
.stab.active em{color:#ffffffcc}
.subject-block{margin-bottom:38px}
.subject-head{display:flex;align-items:baseline;gap:12px;margin-bottom:16px}
.subject-head h2{font-size:21px}
.subject-count{font-size:13px;color:var(--muted);font-weight:700}
.lesson-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:14px}
.lesson-card{
  display:flex;align-items:center;gap:14px;background:var(--card);
  border:2px solid var(--line);border-radius:16px;padding:16px 18px;
  box-shadow:var(--shadow);transition:.2s;position:relative;overflow:hidden;
}
.lesson-card::before{
  content:'';position:absolute;left:0;top:0;bottom:0;width:5px;
  background:var(--grad-hero);opacity:0;transition:.2s;
}
.lesson-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-lg);border-color:#bcd0f5}
.lesson-card:hover::before{opacity:1}
.lc-num{
  font-size:21px;font-weight:900;color:#c3d0ee;min-width:40px;text-align:center;
  font-variant-numeric:tabular-nums;
}
.lesson-card:hover .lc-num{color:var(--blue)}
.lc-body{flex:1;min-width:0}
.lc-title{font-weight:800;font-size:15px;margin-bottom:6px;line-height:1.4}
.lc-meta{display:flex;gap:6px;flex-wrap:wrap}
.tag{font-size:11.5px;font-weight:700;border-radius:999px;padding:2px 10px}
.tag-ok{background:#e9f9f0;color:#1d8a52}
.tag-dev{background:#f2f6ff;color:#7a86a5}
.tag-lock{background:#fdeeec;color:var(--red)}
.lc-arrow{font-size:18px;color:var(--muted);flex:0 0 auto}
/* 锁定课程 */
.lesson-card.locked{background:#f4f6fa;cursor:not-allowed;filter:grayscale(.35)}
.lesson-card.locked .lc-title{color:#8a97b4}
.lesson-card.locked:hover{transform:none;box-shadow:var(--shadow);border-color:var(--line)}
.lesson-card.locked:hover::before{opacity:0}
.lesson-card.locked .lc-arrow{color:#b6c0d8}
.hall-foot{text-align:center;color:var(--muted);font-size:13.5px;padding:18px 0 6px}

/* ============ 课程页眉 ============ */
.lesson-hero{background:var(--grad-hero);color:#fff}
.lh-inner{max-width:1100px;margin:0 auto;padding:34px 20px 30px}
.lh-crumb{font-size:13px;opacity:.85;margin-bottom:10px}
.lh-crumb a{border-bottom:1px dashed #ffffff88}
.lesson-hero h1{font-size:clamp(22px,3.4vw,32px);margin-bottom:12px}
.lh-chips{display:flex;gap:10px;flex-wrap:wrap}

/* ============ 上一讲/下一讲 ============ */
.lesson-main{max-width:1100px;margin:0 auto;padding:8px 20px}
.lesson-pager{
  max-width:1100px;margin:26px auto 0;padding:0 20px;
  display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap;
}
.pager-btn{
  flex:1;min-width:240px;background:var(--card);border:2px solid var(--line);border-radius:16px;
  padding:14px 20px;box-shadow:var(--shadow);transition:.2s;
}
.pager-btn:hover{border-color:var(--blue);transform:translateY(-2px)}
.pager-next{text-align:right}
.pager-dir{display:block;font-size:12.5px;color:var(--muted);font-weight:700;margin-bottom:3px}
.pager-title{font-weight:800;font-size:14.5px;color:var(--ink-soft)}

/* ============ 页脚 ============ */
.page-foot{
  max-width:1100px;margin:30px auto 0;padding:22px 20px 34px;text-align:center;
  color:var(--muted);font-size:14px;display:flex;flex-direction:column;gap:4px;
}

/* ============ 弹窗 / 提示 ============ */
.modal-mask{
  position:fixed;inset:0;background:rgba(24,32,56,.45);backdrop-filter:blur(3px);
  display:none;align-items:center;justify-content:center;z-index:100;padding:20px;
}
.modal-mask.show{display:flex;animation:fadeIn .25s}
.modal{
  background:#fff;border-radius:20px;padding:32px 34px;max-width:420px;width:100%;
  text-align:center;box-shadow:var(--shadow-lg);animation:pop .35s cubic-bezier(.2,.9,.3,1.4);
}
.modal-icon{font-size:44px;margin-bottom:8px}
.modal h3{font-size:19px;margin-bottom:10px}
.modal p{color:var(--ink-soft);font-size:15px;margin-bottom:20px}
.modal-btn{
  background:var(--grad-hero);color:#fff;border:none;border-radius:12px;
  padding:11px 34px;font-size:15px;font-weight:800;cursor:pointer;box-shadow:0 5px 14px rgba(59,111,224,.3);
}
@keyframes fadeIn{from{opacity:0}to{opacity:1}}
@keyframes pop{from{transform:scale(.7);opacity:0}to{transform:scale(1);opacity:1}}
.toast{
  position:fixed;top:70px;left:50%;transform:translateX(-50%) translateY(-12px);
  background:var(--ink);color:#fff;border-radius:12px;padding:11px 22px;font-size:14.5px;
  font-weight:700;box-shadow:var(--shadow-lg);opacity:0;transition:.3s;z-index:120;pointer-events:none;
}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}

/* ============ 登录页 ============ */
.login-body{background:var(--grad-hero);min-height:100vh;display:flex;align-items:center;justify-content:center;padding:20px}
.login-bg{position:fixed;inset:0;overflow:hidden;pointer-events:none}
.orb{position:absolute;border-radius:50%;background:rgba(255,255,255,.08);animation:float 9s ease-in-out infinite}
.orb-1{width:340px;height:340px;top:-100px;left:-80px}
.orb-2{width:240px;height:240px;bottom:-60px;right:-60px;animation-delay:2.5s}
.orb-3{width:150px;height:150px;top:38%;right:16%;animation-delay:5s}
@keyframes float{0%,100%{transform:translateY(0)}50%{transform:translateY(-26px)}}
.login-wrap{position:relative;width:100%;max-width:430px;z-index:2}
.login-card{
  background:#ffffff;border-radius:24px;padding:42px 40px 30px;
  box-shadow:0 24px 60px rgba(10,20,50,.35);animation:pop .45s cubic-bezier(.2,.9,.3,1.4);
}
.login-brand{text-align:center;margin-bottom:28px}
.login-logo{width:84px;height:84px;border-radius:22px;object-fit:cover;box-shadow:0 8px 22px rgba(59,111,224,.3);margin-bottom:14px}
.login-brand h1{font-size:21px;line-height:1.4}
.login-sub{font-size:12px;color:var(--muted);letter-spacing:2.5px;margin-top:6px}
.login-error{
  background:#fdeeec;border:1.5px solid #f5c6bd;color:var(--red);
  border-radius:12px;padding:10px 16px;font-size:14px;font-weight:700;margin-bottom:18px;text-align:center;
}
.field{display:block;margin-bottom:16px}
.field-label{display:block;font-size:13.5px;font-weight:800;color:var(--ink-soft);margin-bottom:7px}
.field input{
  width:100%;border:2.5px solid var(--line);border-radius:12px;padding:12px 16px;
  font-size:15px;font-family:inherit;transition:.2s;background:#fbfcff;color:var(--ink);
}
.field input:focus{outline:none;border-color:var(--blue);background:#fff;box-shadow:0 0 0 4px rgba(59,111,224,.12)}
.login-btn{
  width:100%;border:none;border-radius:12px;padding:13px;font-size:16.5px;font-weight:900;
  color:#fff;background:var(--grad-hero);cursor:pointer;margin-top:6px;
  box-shadow:0 6px 18px rgba(59,111,224,.35);transition:.2s;letter-spacing:6px;
}
.login-btn:hover{transform:translateY(-2px);box-shadow:0 9px 24px rgba(59,111,224,.45)}
.login-foot{text-align:center;font-size:12.5px;color:var(--muted);margin-top:22px}

/* ============ 制作中占位页 ============ */
.coming{max-width:760px;margin:30px auto;text-align:center}
.coming .card{
  background:var(--card);border:2px solid var(--line);border-radius:22px;
  padding:56px 40px;box-shadow:var(--shadow);
}
.coming-icon{font-size:64px;margin-bottom:16px;animation:float 4s ease-in-out infinite}
.coming h2{font-size:24px;margin-bottom:12px}
.coming p{color:var(--ink-soft);font-size:15.5px;max-width:520px;margin:0 auto 24px}
.coming-list{display:flex;gap:10px;justify-content:center;flex-wrap:wrap;margin-bottom:26px}
.coming-list span{
  background:#f2f6ff;border:1.5px solid var(--line);border-radius:999px;
  padding:6px 16px;font-size:13px;font-weight:700;color:var(--ink-soft);
}
.denied-box{border:2.5px dashed #f5c6bd;background:#fff7f5;border-radius:18px;padding:26px 30px;margin-bottom:24px}
.denied-box h3{color:var(--red);font-size:18px;margin-bottom:8px}
.denied-box p{color:var(--ink-soft)}

/* ============================================================
   课件播放器（所有课程通用，源自单链表课件引擎）
   ============================================================ */
.lesson{max-width:1100px;margin:0 auto;padding:38px 20px 6px}
.lesson-head{display:flex;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:6px}
.lesson-pill{
  background:var(--blue);color:#fff;font-weight:800;font-size:14px;
  border-radius:999px;padding:5px 16px;box-shadow:0 3px 8px rgba(59,111,224,.3);
}
.lesson h2{font-size:clamp(20px,3vw,27px)}
.lesson h3{margin:18px 0 8px;font-size:18px}
.lead{color:var(--ink-soft);font-size:16.5px;margin:8px 0 18px;max-width:900px}
.lead b{color:var(--blue-d)}
.card{background:var(--card);border:2px solid var(--line);border-radius:18px;overflow:hidden;box-shadow:var(--shadow)}
.tip{
  background:#fff8ec;border:2px dashed #ffd08a;border-radius:12px;
  padding:10px 16px;font-size:14.5px;color:#8a5b16;margin-top:14px;
}
.player .stage{background:#fbfdff;padding:8px 6px;position:relative;min-height:150px}
.stage{position:relative}
.stage-tip{display:flex;align-items:center;justify-content:center;min-height:130px;color:var(--muted);font-size:17px;font-weight:700;text-align:center;padding:20px}
.explain{
  padding:16px 20px;font-size:17px;line-height:1.85;border-top:2px dashed var(--line);
  min-height:86px;background:#fff;
}
.explain b{color:var(--accent-d)}
.explain .g{color:var(--green);font-weight:800}
.explain .r{color:var(--red);font-weight:800}
.controls{
  display:flex;align-items:center;justify-content:center;gap:12px;flex-wrap:wrap;
  padding:14px;background:#f7f9ff;border-top:2px solid var(--line);
}
.p-count{font-weight:800;color:var(--muted);font-size:14px;min-width:56px;text-align:center}
.btn.p-auto{background:#e6f7ee;color:#1d8a52}
.btn.p-auto.on{background:#1d8a52;color:#fff}
.btn.btn-primary{background:var(--blue);color:#fff}

/* —— 链表节点 —— */
.chain{display:flex;align-items:center;padding:46px 14px 20px;overflow-x:auto;min-height:150px;gap:46px;position:relative}
.chain.center{justify-content:center}
.node{
  flex:0 0 auto;min-width:88px;border:3px solid var(--ink);border-radius:12px;background:#fff;
  box-shadow:0 4px 0 rgba(31,42,68,.14);
}
.node .data{padding:10px 14px;font-size:23px;font-weight:900;text-align:center}
.node .ptr{
  border-top:2px dashed #c6cede;font-size:11px;color:var(--muted);text-align:center;
  padding:4px 6px;background:#f6f8ff;border-radius:0 0 9px 9px;letter-spacing:1px;
}
.node.new{border-style:dashed;border-color:var(--accent)}
.node.new .data{color:var(--accent-d)}
.node.cur{border-color:var(--blue);box-shadow:0 0 0 5px rgba(59,111,224,.22)}
.node.doomed{border-color:var(--red);background:#fff1ee}
.node.doomed .data{color:var(--red);text-decoration:line-through}
.node.dim{opacity:.38}
.anim-pop{animation:pop .5s cubic-bezier(.2,.9,.3,1.4)}
@keyframes pop2{from{transform:scale(.35);opacity:0}to{transform:scale(1);opacity:1}}
.overlay-svg{position:absolute;left:0;top:0;pointer-events:none;overflow:visible;z-index:5}
.c-arrow{fill:none;stroke:#5a6b95;stroke-width:3;stroke-linecap:round}
.c-arrow.hl{stroke:#ff8f2b;stroke-width:4.5}
.c-arrow.green{stroke:#2fbf71;stroke-width:4.5}
.c-arrow.blue{stroke:#3b6fe0;stroke-width:4.5}
.c-arrow.red{stroke:#e5533d;stroke-width:3.5;stroke-dasharray:7 6}
.c-arrow.dim{opacity:.28}
.head-block{flex:0 0 auto}
.head-pill{
  display:inline-block;background:var(--green);color:#fff;font-weight:900;
  padding:7px 14px;border-radius:999px;font-size:14px;box-shadow:0 3px 8px rgba(47,191,113,.35);
}
.head-block.hl .head-pill{box-shadow:0 0 0 5px rgba(47,191,113,.3)}
.head-block.hl{animation:pop .5s}
.null-tag{
  flex:0 0 auto;border:3px dashed #9aa7c7;color:var(--muted);font-weight:800;
  padding:10px 13px;border-radius:10px;background:#f4f6fb;font-family:Consolas,monospace;font-size:15px;
}
.null-tag.hl{border-color:var(--accent);color:var(--accent-d);animation:pop .5s}
.empty-tip{display:flex;align-items:center;justify-content:center;min-height:120px;color:var(--muted);font-weight:700;font-size:16px}

/* —— 数组格子 —— */
.cells{display:flex;gap:9px;padding:34px 12px 24px;justify-content:center;flex-wrap:wrap}
.cell{width:66px;text-align:center}
.cell .box{
  height:58px;border:3px solid var(--ink);border-radius:11px;background:#fff;
  display:flex;align-items:center;justify-content:center;font-size:21px;font-weight:900;
  box-shadow:0 4px 0 rgba(31,42,68,.12);
}
.cell .idx{font-size:12px;color:var(--muted);margin-top:5px;font-weight:700}
.cell.empty .box{border-style:dashed;background:#f4f6fb;color:#b6c0d8}
.cell.moving .box{border-color:var(--accent);color:var(--accent-d);animation:pop .5s}
.cell.placed .box{border-color:var(--green);color:#1d8a52;background:#eefbf3;animation:pop .5s}
.cell.target .box{border-color:var(--accent);background:#fff6ea;color:var(--accent-d)}

/* —— 代码播放器（通用） —— */
.cp-wrap{display:grid;grid-template-columns:1.25fr .75fr;min-height:300px}
@media (max-width:820px){.cp-wrap{grid-template-columns:1fr}}
.cp-code{background:#1e2740;padding:18px 8px 18px 0;overflow:auto}
.cp-code pre{margin:0;display:block}
.cl{
  font-family:Consolas,"Courier New",monospace;font-size:14.5px;line-height:1.9;
  color:#c8d3ef;padding:0 18px 0 24px;white-space:pre;position:relative;display:block;
}
.cl.hl-line{background:rgba(255,143,43,.16);color:#ffe9d1}
.cl.hl-line::before{content:'▸';position:absolute;left:8px;color:var(--accent)}
.cl .k{color:#7fb2ff;font-weight:700}
.cl .c{color:#7ee2a8}
.cl .s{color:#ffd58a}
.cl .n{color:#ff9d9d}
.cl .f{color:#9fe8ff}
.cp-side{display:flex;flex-direction:column;background:#141b30;border-left:2px solid #2a3654}
.cp-side-title{
  color:#8fa1c9;font-size:12.5px;font-weight:800;letter-spacing:2px;
  padding:12px 18px 8px;border-bottom:1.5px dashed #2a3654;
}
.cp-console{
  flex:1;padding:14px 18px;font-family:Consolas,"Courier New",monospace;font-size:15px;
  color:#7ee2a8;white-space:pre-wrap;word-break:break-all;min-height:120px;
}
.cp-console::after{content:'▊';color:#7ee2a8;animation:blink 1s steps(1) infinite}
@keyframes blink{50%{opacity:0}}

/* —— 代码卡片 —— */
.code-card{background:#1e2740;padding:18px 20px;overflow-x:auto}
.code-card pre{margin:0}
.code-card code{font-family:Consolas,"Courier New",monospace;font-size:14.5px;line-height:1.75;color:#e8edfa;white-space:pre}
.code-card .k{color:#7fb2ff;font-weight:700}
.code-card .c{color:#7ee2a8}
.code-card .s{color:#ffd58a}

/* —— 知识总结 —— */
.sum-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:16px}
.sum-card{padding:18px 20px}
.sum-card h4{font-size:16px;margin-bottom:10px}
.sum-card ul{list-style:none}
.sum-card li{padding:5px 0 5px 22px;position:relative;font-size:14.5px}
.sum-card li::before{content:"✔";position:absolute;left:0;color:var(--green);font-weight:900}
table.cmp{width:100%;border-collapse:collapse;font-size:14px}
table.cmp th,table.cmp td{border:1.5px solid var(--line);padding:7px 9px;text-align:center}
table.cmp th{background:#f2f6ff}
table.cmp .good{color:#1d8a52;font-weight:700}
table.cmp .bad{color:var(--red);font-weight:700}

/* —— 测验 —— */
.quiz-card{padding:6px 20px 16px}
.q-item{padding:16px 0;border-bottom:2px dashed var(--line)}
.q-item:last-of-type{border-bottom:none}
.q-title{font-weight:800;font-size:15.5px;margin-bottom:10px}
.q-opts{display:flex;gap:10px;flex-wrap:wrap}
.q-opt{border:2px solid var(--line);background:#fff;border-radius:10px;padding:8px 16px;font-size:14.5px;font-weight:600;cursor:pointer;transition:.15s}
.q-opt:hover{border-color:var(--blue)}
.q-item.done .q-opt{cursor:default}
.q-opt.right{border-color:var(--green);background:#e9f9f0;color:#1d8a52;font-weight:800}
.q-opt.wrong{border-color:var(--red);background:#fdeeec;color:var(--red)}
.q-explain{margin-top:10px;font-size:14px;color:var(--ink-soft);background:#f7f9ff;border-radius:10px;padding:8px 12px;display:none}
.q-item.done .q-explain{display:block}
.quiz-foot{display:flex;align-items:center;justify-content:space-between;gap:12px;padding-top:14px;border-top:2px solid var(--line);margin-top:6px}
.quiz-score{font-weight:900;font-size:17px;color:var(--blue-d)}

/* —— 实验室 —— */
.lab-bar{display:flex;gap:10px;flex-wrap:wrap;padding:14px 16px;border-bottom:2px solid var(--line);background:#f7f9ff}
.lab-op{background:#e9eefb}
.lab-op:hover{background:#d9e4fa}
.lab-output{
  max-width:640px;margin:2px auto 14px;background:#1e2740;color:#7ee2a8;
  font-family:Consolas,monospace;font-size:15px;padding:9px 16px;border-radius:10px;
}

/* —— 节点解剖 —— */
.anatomy{display:flex;align-items:center;justify-content:center;gap:26px;flex-wrap:wrap;padding:40px 16px}
.big-node{display:flex;border:4px solid var(--ink);border-radius:16px;overflow:hidden;background:#fff;box-shadow:0 6px 0 rgba(31,42,68,.15)}
.bn{padding:20px 28px;text-align:center;min-width:160px}
.bn .bn-label{font-size:13px;color:var(--muted);font-weight:700;margin-bottom:8px}
.bn .bn-val{font-size:26px;font-weight:900}
.bn.data{background:#eef4ff}
.bn.ptr{background:#fff4e6;border-left:3px dashed #c6cede}
.big-node.hl-data .bn.data{background:#cfe1ff;box-shadow:inset 0 0 0 4px var(--blue)}
.big-node.hl-ptr .bn.ptr{background:#ffe3bd;box-shadow:inset 0 0 0 4px var(--accent)}
.anatomy-arrow{font-size:34px;color:var(--accent);font-weight:900}
.mini-node{border:3px solid var(--ink);border-radius:12px;padding:14px 18px;font-weight:800;background:#f6f8ff}
.struct-code{max-width:520px;margin:18px auto 0}

/* —— 课件内导航 —— */
.lnav{display:flex;gap:6px;flex-wrap:wrap;justify-content:center;padding:8px 16px}
.lnav button{
  border:2px solid var(--line);background:#fff;color:var(--ink);
  padding:7px 13px;border-radius:999px;font-size:13.5px;font-weight:700;cursor:pointer;transition:.2s;
}
.lnav button:hover{border-color:var(--blue);color:var(--blue)}
.lnav button.active{background:var(--blue);border-color:var(--blue);color:#fff}

@media (max-width:720px){
  .bn{min-width:120px;padding:14px 16px}
  .bn .bn-val{font-size:20px}
  .topbar{padding:10px 14px}
  .hero-inner{padding:40px 16px 34px}
}