/* ============================================================
   炸弹人学院 · 课程页统一样式系统  v2.0
   加载于各页内联 <style> 之后,负责:
   1. 修复设计令牌(--school 自引用失效等问题)
   2. 统一的排版比例 / 间距节奏 / 圆角与阴影规范
   3. PC + 手机全端响应式适配
   ============================================================ */

/* ---------- 设计令牌 ---------- */
:root{
  --bg:#0d1017; --bg2:#0a0c12;
  --card:#151a26; --card2:#1b2231;
  --line:#28324c; --line-soft:rgba(40,50,76,.55);
  --txt:#e8ebf2; --dim:#99a1b4; --faint:#6b7280;
  --acc:#6c8cff; --acc2:#38d9a9;
  --school:#f59e0b; --school2:#fbbf24; --warn:#ffb454;
  --bad:#ff6b81; --good:#51e08c; --blue:#6c8cff; --red:#ff6b81;
  --r-s:8px; --r-m:14px; --r-l:18px;
  --shadow-1:0 1px 3px rgba(0,0,0,.3);
  --shadow-2:0 8px 28px rgba(0,0,0,.32);
  --font-body:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Segoe UI",system-ui,-apple-system,sans-serif;
  --font-mono:"JetBrains Mono","SFMono-Regular",Consolas,"Courier New",monospace;
}

/* ---------- 基础 ---------- */
html{scroll-behavior:smooth; -webkit-text-size-adjust:100%;}
body{
  font-family:var(--font-body);
  font-size:15.5px; line-height:1.8;
  color:var(--txt); background:var(--bg);
  padding-bottom:64px;
  text-rendering:optimizeLegibility;
}
img,canvas,svg,video{max-width:100%;}
canvas{display:block;}
p{overflow-wrap:break-word;}
b,strong{color:var(--txt);}
::selection{background:rgba(245,158,11,.28);}

/* 锚点定位补偿( sticky 导航 ) */
.section,[id]{scroll-margin-top:76px;}

/* ---------- 顶部导航 ---------- */
.topnav{
  position:sticky; top:0; z-index:100;
  display:flex; align-items:center; gap:16px;
  padding:12px 24px;
  background:rgba(13,16,23,.9); backdrop-filter:blur(14px); -webkit-backdrop-filter:blur(14px);
  border-bottom:1px solid var(--line);
}
.topnav .brand{display:flex; align-items:center; gap:10px; text-decoration:none; color:var(--txt); flex-shrink:0;}
.topnav .brand img{width:34px; height:34px; border-radius:9px;}
.topnav .brand b{font-size:15px; color:var(--school); letter-spacing:.5px;}
.topnav .brand small{display:block; font-size:11px; color:var(--dim); font-weight:400; margin-top:1px;}
.topnav .nav-links{
  display:flex; gap:4px; margin-left:auto;
  overflow-x:auto; -webkit-overflow-scrolling:touch; scrollbar-width:none;
}
.topnav .nav-links::-webkit-scrollbar{display:none;}
.topnav .nav-links a{
  color:var(--dim); text-decoration:none; font-size:13.5px;
  padding:6px 12px; border-radius:8px; white-space:nowrap;
  transition:color .18s, background .18s;
}
.topnav .nav-links a:hover{color:var(--txt); background:var(--card2);}
.topnav .nav-links a.active{color:var(--school); background:rgba(245,158,11,.12);}
.topnav .home-link{
  flex-shrink:0; color:var(--acc); text-decoration:none; font-size:13px;
  padding:6px 14px; border:1px solid var(--line); border-radius:8px;
  transition:border-color .18s, background .18s; white-space:nowrap;
}
.topnav .home-link:hover{border-color:var(--acc); background:rgba(108,140,255,.08);}

/* ---------- HERO ---------- */
.hero{
  text-align:center; position:relative; overflow:hidden;
  padding:56px 24px 44px; max-width:880px; margin:0 auto;
}
.hero .badge{
  display:inline-flex; align-items:center; gap:6px;
  background:rgba(245,158,11,.12); color:var(--school);
  border:1px solid rgba(245,158,11,.32); border-radius:999px;
  padding:5px 16px; font-size:13px; font-weight:600; margin-bottom:20px;
}
.hero h1{
  font-size:clamp(30px,5.5vw,46px); font-weight:800; letter-spacing:.5px;
  line-height:1.25; margin:0 0 16px;
  background:linear-gradient(135deg,var(--school) 0%,var(--school2) 55%,var(--warn) 100%);
  -webkit-background-clip:text; background-clip:text; color:transparent;
}
.hero .sub{
  font-size:clamp(14.5px,2.2vw,17px); color:var(--dim);
  line-height:1.75; max-width:640px; margin:0 auto 20px;
}
.hero .meta{
  display:flex; justify-content:center; gap:10px 22px; flex-wrap:wrap;
  font-size:13px; color:var(--dim);
}
.hero .meta span{display:inline-flex; align-items:center; gap:6px;}

/* ---------- 布局骨架 ---------- */
.wrap{max-width:var(--maxw,1080px); margin:0 auto; padding:0 24px;}
.section{margin:56px 0;}
.section-title{
  display:flex; align-items:center; gap:14px; flex-wrap:wrap;
  margin-bottom:26px; padding-bottom:14px;
  font-size:21px; font-weight:700; line-height:1.4;
  border-bottom:1px solid var(--line);
}
.section-title .num{
  width:38px; height:38px; border-radius:12px; flex-shrink:0;
  display:flex; align-items:center; justify-content:center;
  font-size:17px; font-weight:800; color:#0d1017;
  background:linear-gradient(135deg,var(--school),var(--warn));
  box-shadow:0 3px 10px rgba(245,158,11,.3);
}
.section-title .hint{
  margin-left:auto; font-size:12.5px; color:var(--dim); font-weight:400;
}

/* ---------- 卡片 ---------- */
.card{
  background:var(--card); border:1px solid var(--line); border-radius:var(--r-l);
  padding:26px 28px; margin-bottom:20px; box-shadow:var(--shadow-1);
  transition:transform .22s ease, box-shadow .22s ease, border-color .22s ease;
}
.card:hover{transform:translateY(-2px); box-shadow:var(--shadow-2); border-color:rgba(108,140,255,.35);}
.card h3{font-size:17px; font-weight:700; margin:0 0 12px; display:flex; align-items:center; gap:9px; line-height:1.5;}
.card h3 .emoji{font-size:19px;}
.card p{color:var(--dim); font-size:14.5px; margin:0 0 10px;}
.card p:last-child{margin-bottom:0;}
.card ul,.card ol{color:var(--dim); font-size:14.5px; padding-left:22px; margin:8px 0;}
.card li{margin:5px 0;}

/* ---------- 学习目标 ---------- */
.objectives{
  background:linear-gradient(135deg,rgba(245,158,11,.09),rgba(108,140,255,.07));
  border:1px solid rgba(245,158,11,.28); border-radius:var(--r-l);
  padding:26px 28px; margin-bottom:40px;
}
.objectives h3{font-size:17px; font-weight:700; margin:0 0 14px; display:flex; align-items:center; gap:9px;}
.objectives ul{list-style:none; padding:0; margin:0; display:grid; gap:10px;}
.objectives li{
  font-size:14.5px; color:var(--dim); line-height:1.7;
  display:flex; align-items:flex-start; gap:10px;
}
.objectives li::before{content:'✅'; flex-shrink:0; font-size:14px; margin-top:2px;}

/* ---------- 游戏演示区 ---------- */
.game-section{
  background:linear-gradient(180deg,var(--card) 0%,var(--bg2) 130%);
  border:1px solid var(--line); border-radius:var(--r-l);
  padding:26px 28px; box-shadow:var(--shadow-1);
}
.game-section h3{font-size:17px; font-weight:700; margin:0 0 8px; display:flex; align-items:center; gap:9px;}
.game-section .game-desc{color:var(--dim); font-size:14px; margin:0 0 18px; line-height:1.75;}
.game-layout{display:grid; grid-template-columns:1fr; gap:16px; margin-top:16px;}
@media(min-width:860px){
  .game-layout.lower{grid-template-columns:210px 1fr 1fr; gap:18px;}
}
.game-canvas-wrap{
  background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m);
  overflow:hidden; position:relative;
}
#gameCanvas,#expCanvas,#graphCanvas{width:100%; display:block; image-rendering:pixelated;}
#fieldCanvas,#speedoCanvas{width:100%; height:auto; display:block;}
#gameCanvas{height:220px;}
#graphCanvas{height:240px;}
#expCanvas{height:300px; background:var(--bg2); border-radius:var(--r-m);}
.game-canvas-wrap .hud{
  position:absolute; top:10px; left:10px; right:10px;
  display:flex; justify-content:space-between; gap:8px; pointer-events:none;
}
.game-canvas-wrap .hud span{
  background:rgba(0,0,0,.62); padding:4px 12px; border-radius:8px;
  font-size:12px; font-family:var(--font-mono);
}

/* 按钮组 */
.controls{display:flex; flex-wrap:wrap; gap:10px; margin:18px 0 6px;}
.controls button{
  background:var(--card2); color:var(--txt);
  border:1px solid var(--line); border-radius:10px;
  padding:10px 18px; font-size:14px; font-family:inherit;
  cursor:pointer; user-select:none; touch-action:manipulation;
  min-height:44px; transition:all .18s ease;
}
.controls button:hover{border-color:var(--acc); transform:translateY(-1px); box-shadow:0 4px 14px rgba(108,140,255,.22);}
.controls button:active{transform:scale(.96);}
.controls button.active{background:var(--school); color:#12100a; border-color:var(--school); font-weight:700;}
.controls button.action{background:var(--acc); color:#fff; border-color:var(--acc); font-weight:700;}
.controls button.action:hover{filter:brightness(1.12); box-shadow:0 4px 16px rgba(108,140,255,.38);}
.controls button.reset{background:transparent;}

/* 实时统计 */
.stats{display:grid; grid-template-columns:repeat(3,1fr); gap:10px; align-content:start;}
@media(min-width:860px){.stats{grid-template-columns:1fr;}}
.stat-box{
  background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m);
  padding:14px 10px; text-align:center;
}
.stat-box .label{font-size:12px; color:var(--dim); margin-bottom:4px;}
.stat-box .value{font-size:22px; font-weight:700; font-family:var(--font-mono); line-height:1.3;}

/* 数据表 */
.data-table-wrap{
  background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m);
  padding:14px; max-height:280px; overflow:auto; -webkit-overflow-scrolling:touch;
}
.data-table-wrap h4,.graph-wrap h4{
  font-size:13px; color:var(--dim); font-weight:600;
  margin:0 0 12px; text-align:center; letter-spacing:.3px;
}
.data-table-wrap table{width:100%; border-collapse:collapse; font-family:var(--font-mono); font-size:13px; min-width:200px;}
.data-table-wrap th{
  color:var(--school); text-align:center; padding:6px 8px;
  border-bottom:1px solid var(--line); position:sticky; top:-14px; background:var(--bg2);
}
.data-table-wrap td{text-align:center; padding:5px 8px; color:var(--txt); border-bottom:1px solid var(--line-soft);}
.data-table-wrap tr.latest td{background:rgba(245,158,11,.1); color:var(--school2);}
.graph-wrap{background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m); padding:14px;}

/* ---------- 概念讲解 ---------- */
.formula{
  background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m);
  padding:16px 20px; margin:16px 0;
  font-family:var(--font-mono); font-size:15px; color:var(--acc2);
  overflow-x:auto; line-height:1.9; -webkit-overflow-scrolling:touch;
}
.def-box{
  background:rgba(108,140,255,.06); border:1px solid rgba(108,140,255,.22);
  border-radius:var(--r-m); padding:20px 22px; margin:16px 0;
}
.def-box .def-title{
  color:var(--acc); font-weight:700; font-size:15px;
  margin-bottom:10px; display:flex; align-items:center; gap:7px;
}
.def-box p{color:var(--dim); font-size:14.5px; line-height:1.8; margin:0 0 8px;}
.def-box p:last-child{margin-bottom:0;}
.mapping-grid{display:grid; grid-template-columns:repeat(auto-fit,minmax(230px,1fr)); gap:14px; margin-top:16px;}
.mapping-item{
  background:var(--card2); border:1px solid var(--line); border-radius:var(--r-m);
  padding:16px 18px; transition:border-color .2s;
}
.mapping-item:hover{border-color:rgba(245,158,11,.4);}
.mapping-item .mi-title{font-size:14px; color:var(--school); font-weight:700; margin-bottom:8px;}
.mapping-item .mi-game{font-size:13.5px; color:var(--dim); margin-bottom:6px; line-height:1.65;}
.mapping-item .mi-arrow{color:var(--acc); font-size:12px; margin:6px 0;}
.mapping-item .mi-math{font-family:var(--font-mono); font-size:14px; color:var(--acc2); line-height:1.7;}
.knowledge-card{
  background:linear-gradient(135deg,var(--card),var(--card2));
  border:1px solid var(--line); border-radius:var(--r-m);
  padding:20px 22px 20px 24px; margin:14px 0; position:relative; overflow:hidden;
}
.knowledge-card::before{
  content:""; position:absolute; top:0; left:0; width:4px; height:100%;
  background:linear-gradient(180deg,var(--school),var(--warn));
}

/* ---------- 互动实验 ---------- */
.experiment{
  background:var(--card); border:1px solid var(--line); border-radius:var(--r-l);
  padding:26px 28px; box-shadow:var(--shadow-1);
}
.experiment h3{font-size:17px; font-weight:700; margin:0 0 8px; display:flex; align-items:center; gap:9px;}
.slider-row{display:flex; align-items:center; gap:14px; margin:18px 0; flex-wrap:wrap;}
.slider-row label{font-size:14px; color:var(--dim); min-width:56px;}
.slider-row input[type=range]{flex:1; min-width:160px; height:6px; accent-color:var(--school); cursor:pointer;}
.slider-row .k-val{
  font-family:var(--font-mono); font-size:16px; font-weight:700; color:var(--school);
  min-width:52px; text-align:center;
}
.exp-eq{
  text-align:center; font-family:var(--font-mono); font-size:18px;
  margin:18px 0; padding:16px; background:var(--bg2); border-radius:var(--r-m);
  overflow-x:auto;
}
.exp-insight{
  background:rgba(245,158,11,.07); border:1px solid rgba(245,158,11,.22);
  border-radius:var(--r-m); padding:12px 16px; margin-top:14px;
  font-size:13.5px; color:var(--school2); line-height:1.7;
}

/* ---------- 测验关卡 ---------- */
.quiz{
  background:var(--card); border:1px solid var(--line); border-radius:var(--r-l);
  padding:26px 28px; box-shadow:var(--shadow-1);
}
.quiz-q{margin-bottom:26px;}
.quiz-q:last-of-type{margin-bottom:18px;}
.quiz-q .q-num{
  display:inline-flex; align-items:center; justify-content:center;
  width:26px; height:26px; border-radius:50%;
  background:var(--school); color:#12100a;
  font-size:13px; font-weight:800; margin-right:9px; vertical-align:2px;
}
.quiz-q .q-text{font-size:15px; font-weight:600; line-height:1.7;}
.quiz-q .q-context{font-size:13.5px; color:var(--dim); margin:8px 0 12px 36px; line-height:1.7;}
.quiz-options{display:flex; flex-direction:column; gap:10px; margin-left:36px;}
.quiz-opt{
  background:var(--card2); border:1px solid var(--line); border-radius:10px;
  padding:11px 16px; font-size:14px; text-align:left;
  font-family:inherit; color:var(--txt); line-height:1.6;
  cursor:pointer; user-select:none; touch-action:manipulation;
  min-height:44px; transition:transform .16s, border-color .16s, background .16s, box-shadow .16s;
}
.quiz-opt:hover{border-color:var(--acc); transform:translateX(4px); box-shadow:0 2px 10px rgba(108,140,255,.18);}
.quiz-opt.correct{border-color:var(--good); background:rgba(81,224,140,.1); color:var(--good);}
.quiz-opt.wrong{border-color:var(--bad); background:rgba(255,107,129,.1); color:var(--bad);}
.quiz-opt:disabled{cursor:default;}
.quiz-opt:disabled:hover{transform:none; box-shadow:none;}
.quiz-feedback{margin:10px 0 0 36px; font-size:13.5px; font-weight:600; min-height:22px; line-height:1.6;}
.quiz-feedback.ok{color:var(--good);}
.quiz-feedback.no{color:var(--bad);}
.quiz-score{
  text-align:center; margin-top:22px; padding:22px;
  background:rgba(245,158,11,.07); border:1px solid rgba(245,158,11,.22); border-radius:var(--r-m);
}
.quiz-score .big{font-size:30px; font-weight:800; color:var(--school); font-family:var(--font-mono);}
.quiz-score .stars{font-size:20px; letter-spacing:6px; margin-top:8px;}

/* ---------- 小结 / 下一课 / 页脚 ---------- */
.summary{
  background:linear-gradient(135deg,rgba(245,158,11,.09),rgba(108,140,255,.09));
  border:1px solid var(--line); border-radius:var(--r-l); padding:26px 28px;
}
.summary h3{font-size:18px; font-weight:700; margin:0 0 16px; color:var(--school);}
.summary-grid{display:grid; grid-template-columns:repeat(auto-fit,minmax(210px,1fr)); gap:14px;}
.summ-item{background:var(--card); border:1px solid var(--line); border-radius:var(--r-m); padding:18px;}
.summ-item .st{font-size:14px; color:var(--school); font-weight:700; margin-bottom:8px;}
.summ-item .sd{font-size:13.5px; color:var(--dim); line-height:1.7;}
.next-lesson{
  display:flex; align-items:center; justify-content:space-between; gap:16px; flex-wrap:wrap;
  margin-top:28px; padding:20px 24px;
  background:var(--card); border:1px solid var(--line); border-radius:var(--r-m);
}
.next-lesson .nl-text{font-size:14.5px; color:var(--dim); line-height:1.7;}
.next-lesson .nl-text b{color:var(--txt);}
.next-lesson .nl-btn{
  background:var(--acc); color:#fff; text-decoration:none;
  padding:10px 22px; border-radius:10px; font-size:14px; font-weight:600;
  white-space:nowrap; transition:filter .18s, box-shadow .18s;
}
.next-lesson .nl-btn:hover{filter:brightness(1.12); box-shadow:0 4px 14px rgba(108,140,255,.35);}
.footer{
  text-align:center; color:var(--faint); font-size:12.5px;
  margin-top:64px; padding:26px 20px; border-top:1px solid var(--line); line-height:1.8;
}
.footer a{color:var(--acc); text-decoration:none;}

/* ---------- Python 代码区 ---------- */
.code-section{margin:22px 0;}
.code-toggle{
  display:flex; align-items:center; gap:10px;
  padding:14px 18px; cursor:pointer; user-select:none;
  background:var(--card); border:1px solid var(--line); border-radius:var(--r-m);
  transition:border-color .2s;
}
.code-toggle:hover{border-color:var(--acc2);}
.code-toggle .ico{font-size:18px;}
.code-toggle .txt{font-size:14.5px; font-weight:600; color:var(--acc2);}
.code-toggle .sub{font-size:12px; color:var(--dim); margin-left:auto; text-align:right;}
.code-toggle .arrow{color:var(--dim); transition:transform .3s;}
.code-toggle.open .arrow{transform:rotate(180deg);}
.code-content{display:none; margin-top:10px;}
.code-content.open{display:block;}
.code-block{background:var(--bg2); border:1px solid var(--line); border-radius:var(--r-m); overflow:hidden;}
.code-block .head{
  display:flex; align-items:center; justify-content:space-between;
  padding:9px 16px; background:#161b27; border-bottom:1px solid var(--line);
}
.code-block .head .name{font-size:12px; color:var(--dim); font-family:var(--font-mono);}
.code-block .head .copy{
  font-size:11.5px; color:var(--acc); cursor:pointer; user-select:none;
  padding:4px 10px; border:1px solid var(--line); border-radius:6px; transition:background .18s;
}
.code-block .head .copy:hover{background:var(--card2);}
.code-block pre{
  margin:0; padding:16px 18px;
  font-family:var(--font-mono); font-size:13px; line-height:1.75;
  color:var(--txt); overflow-x:auto; white-space:pre; -webkit-overflow-scrolling:touch;
}
.code-output{background:#0b0e15; border:1px solid var(--line); border-radius:var(--r-m); padding:14px 16px; margin-top:10px;}
.code-output .out-title{font-size:11.5px; color:var(--dim); margin-bottom:8px;}
.code-output pre{font-family:var(--font-mono); font-size:12.5px; color:var(--acc2); margin:0; white-space:pre-wrap; line-height:1.7;}

/* ---------- 提示组件 ---------- */
.tip{
  background:rgba(108,140,255,.07); border-left:3px solid var(--acc);
  padding:12px 16px; border-radius:0 var(--r-s) var(--r-s) 0;
  font-size:13.5px; color:var(--dim); margin:12px 0; line-height:1.75;
}
.hint-box{
  background:rgba(56,217,169,.07); border:1px solid rgba(56,217,169,.22);
  border-radius:var(--r-m); padding:12px 16px; margin:12px 0;
  font-size:13.5px; color:var(--dim); line-height:1.75;
}
.highlight-text{background:rgba(245,158,11,.16); padding:1px 7px; border-radius:5px; color:var(--school);}

/* ---------- 讲师浮窗(移动端适配) ---------- */
.teacher-float{
  position:fixed; bottom:20px; right:20px; width:54px; height:54px; border-radius:50%;
  background:linear-gradient(135deg,#6c8cff,#38d9a9); font-size:23px;
  display:flex; align-items:center; justify-content:center;
  cursor:pointer; box-shadow:0 4px 20px rgba(108,140,255,.45);
  z-index:999; border:none; transition:transform .2s;
}
.teacher-float:hover{transform:scale(1.08);}
.teacher-panel{
  position:fixed; bottom:84px; right:20px;
  width:min(380px,calc(100vw - 32px)); max-height:min(540px,calc(100dvh - 120px));
  background:var(--card); border:1px solid var(--line); border-radius:16px;
  box-shadow:0 12px 44px rgba(0,0,0,.5); z-index:998;
  display:none; flex-direction:column; overflow:hidden;
}
.teacher-panel.open{display:flex;}
.teacher-chat{height:auto; flex:1; min-height:0;}
.tc-messages{font-size:13px;}
.tc-bubble{font-size:13px; line-height:1.65;}
.tc-info .tc-name{font-size:13px;}
.tc-input button{font-size:13px;}
.tp-header button{font-size:16px;}

/* ---------- 学习目标(set 系列使用 .learning-objectives) ---------- */
.learning-objectives{
  background:linear-gradient(135deg,rgba(245,158,11,.09),rgba(108,140,255,.07));
  border:1px solid rgba(245,158,11,.28); border-radius:var(--r-l);
  padding:26px 28px; margin:32px 0 40px;
}
.learning-objectives h3{
  font-size:17px; font-weight:700; color:var(--school);
  margin:0 0 14px; display:flex; align-items:center; gap:9px;
}
.learning-objectives ul{list-style:none; padding:0; margin:0; display:grid; gap:10px;}
.learning-objectives li{
  font-size:14.5px; color:var(--dim); line-height:1.7;
  display:flex; align-items:flex-start; gap:10px;
}
.learning-object-points li::before,.learning-objectives li::before{
  content:'✅'; flex-shrink:0; font-size:14px; margin-top:2px;
}

/* ---------- 课内步骤指示条(set 系列) ---------- */
.progress-bar{
  display:flex; align-items:center; gap:10px; flex-wrap:wrap;
  margin:18px 0 4px; font-size:13px; color:var(--dim);
}
.progress-bar .step{
  padding:5px 13px; border:1px solid var(--line); border-radius:999px;
  font-size:12.5px; background:var(--card2); transition:all .2s;
}
.progress-bar .step.active{
  background:rgba(245,158,11,.14); border-color:var(--school);
  color:var(--school); font-weight:600;
}
.progress-bar .step.done{color:var(--good); border-color:rgba(81,224,140,.4);}
.progress-bar .arrow{color:var(--faint); font-size:12px;}

/* ---------- 阅读进度条(JS 注入,内联样式为主) ---------- */
#readProgress{will-change:width;}
/* ---------- 动效 ---------- */
.canvas-loader{
  position:absolute; top:50%; left:50%; transform:translate(-50%,-50%);
  color:var(--dim); font-size:13px;
}
.fade-in{opacity:0; transform:translateY(18px); transition:opacity .55s ease, transform .55s ease;}
.fade-in.visible{opacity:1; transform:translateY(0);}
@media(prefers-reduced-motion:reduce){
  *,*::before,*::after{animation-duration:.01ms!important; transition-duration:.01ms!important;}
  html{scroll-behavior:auto;}
  .fade-in{opacity:1; transform:none;}
}

/* ============================================================
   响应式 — 平板
   ============================================================ */
@media(max-width:860px){
  .wrap{padding:0 18px;}
  .section{margin:44px 0;}
  .section-title{font-size:19px; margin-bottom:22px;}
  .section-title .hint{width:100%; margin-left:52px; margin-top:-6px;}
  .card,.game-section,.experiment,.quiz,.summary,.objectives{padding:20px;}
  .quiz-options,.quiz-q .q-context,.quiz-feedback{margin-left:0;}
  .quiz-q .q-num{vertical-align:1px;}
}

/* ============================================================
   响应式 — 手机
   ============================================================ */
@media(max-width:600px){
  body{font-size:15px; padding-bottom:48px;}
  .topnav{padding:10px 14px; gap:10px; flex-wrap:wrap;}
  .topnav .nav-links{
    display:flex; order:3; width:100%; margin-left:0;
    padding-top:2px;
  }
  .topnav .nav-links a{font-size:13px; padding:5px 10px;}
  .topnav .home-link{margin-left:auto; font-size:12.5px; padding:5px 12px;}
  .hero{padding:40px 18px 32px;}
  .hero .meta{gap:8px 16px; font-size:12.5px;}
  .wrap{padding:0 14px;}
  .section{margin:38px 0;}
  .section-title{gap:11px; padding-bottom:12px;}
  .section-title .num{width:32px; height:32px; font-size:15px; border-radius:10px;}
  .card,.game-section,.experiment,.quiz,.summary,.objectives{padding:18px 16px; border-radius:var(--r-m);}
  .objectives{margin-bottom:32px;}
  .controls{gap:8px;}
  .controls button{flex:1 1 calc(50% - 8px); padding:10px 12px; font-size:13.5px;}
  .controls button.action,.controls button.reset{flex:1 1 100%;}
  #gameCanvas{height:180px;}
  #graphCanvas{height:200px;}
  #expCanvas{height:240px;}
  .stat-box .value{font-size:19px;}
  .formula{font-size:13.5px; padding:14px 16px;}
  .exp-eq{font-size:16px;}
  .quiz-score .big{font-size:26px;}
  .next-lesson{flex-direction:column; align-items:stretch; text-align:center;}
  .next-lesson .nl-btn{display:block; text-align:center;}
  .code-toggle{flex-wrap:wrap;}
  .code-toggle .sub{width:100%; margin-left:28px; text-align:left;}
  .code-block pre{font-size:12px; padding:14px;}
  .teacher-float{bottom:16px; right:16px; width:50px; height:50px;}
  .teacher-panel{bottom:76px; right:12px; width:calc(100vw - 24px);}
  .footer{margin-top:48px;}
}

/* 超小屏 */
@media(max-width:380px){
  .controls button{flex:1 1 100%;}
  .stats{grid-template-columns:repeat(3,1fr); gap:8px;}
  .stat-box{padding:10px 6px;}
  .stat-box .value{font-size:16px;}
}