/* ========== RESET & BASE ========== */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{font-size:16px;scroll-behavior:smooth}
body{font-family:'Segoe UI','PingFang SC','Microsoft YaHei',sans-serif;background:#f0f2f5;color:#2d3748;line-height:1.7;min-height:100vh}

/* ========== LOGO BAR ========== */
.logo-bar{position:fixed;top:0;left:0;right:0;z-index:100;display:flex;align-items:center;padding:10px 28px;background:linear-gradient(135deg,#1a365d 0%,#2c5282 100%);box-shadow:0 2px 12px rgba(0,0,0,.15);height:48px}
.logo-bar img{height:32px;width:auto;object-fit:contain;background:#ffffff;border-radius:6px;padding:2px 8px;box-shadow:0 1px 4px rgba(0,0,0,.25)}
.logo-bar .logo-label{margin-left:12px;font-size:14px;color:rgba(255,255,255,.85);letter-spacing:.5px}
/* 页眉导航：logo 图标→课程主页；页眉文字→本课目录（返回入口，原来几乎不可见） */
.logo-bar .brand-link{display:flex;align-items:center;text-decoration:none;border-radius:8px;padding:2px 4px;transition:background .15s}
.logo-bar .brand-link:hover{background:rgba(255,255,255,.18)}
.logo-bar .toc-link{display:inline-flex;align-items:center;margin-left:12px;font-size:14px;letter-spacing:.5px;
  color:rgba(255,255,255,.92);text-decoration:none;padding:5px 12px;border-radius:9px;
  border:1px solid rgba(255,255,255,.30);background:rgba(255,255,255,.07);transition:all .16s;white-space:nowrap}
.logo-bar .toc-link:hover{background:#fff;color:#1a365d;border-color:#fff}
.logo-bar .toc-link .toc-hint{opacity:0;max-width:0;overflow:hidden;white-space:nowrap;font-size:12.5px;
  transition:all .18s ease;color:inherit}
.logo-bar .toc-link:hover .toc-hint{opacity:.85;max-width:170px;margin-left:10px}
@media (hover:none){ .logo-bar .toc-link .toc-hint{opacity:.85;max-width:170px;margin-left:8px} }

/* ========== HOME PAGE ========== */
.home-container{max-width:1100px;margin:0 auto;padding:100px 24px 60px}
.home-hero{text-align:center;margin-bottom:56px}
.home-hero h1{font-size:clamp(1.6rem,3.5vw,2.4rem);color:#1a365d;font-weight:700;line-height:1.4;margin-bottom:16px}
.home-hero .subtitle{font-size:1.15rem;color:#4a5568;font-weight:400;margin-bottom:8px}
.home-hero .audience{display:inline-block;margin-top:12px;padding:8px 24px;background:#edf2f7;border-radius:20px;font-size:.9rem;color:#4a5568}

.lecture-cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:24px}
.lecture-card{background:#fff;border-radius:16px;overflow:hidden;box-shadow:0 2px 16px rgba(0,0,0,.06);transition:transform .25s,box-shadow .25s;text-decoration:none;color:inherit;display:flex;flex-direction:column}
.lecture-card:hover{transform:translateY(-4px);box-shadow:0 8px 32px rgba(0,0,0,.1)}
.lecture-card .card-banner{height:120px;display:flex;align-items:center;justify-content:center;font-size:2.6rem;font-weight:800;color:#fff}
.lecture-card:nth-child(1) .card-banner{background:linear-gradient(135deg,#2b6cb0,#3182ce)}
.lecture-card:nth-child(2) .card-banner{background:linear-gradient(135deg,#2c7a7b,#38b2ac)}
.lecture-card:nth-child(3) .card-banner{background:linear-gradient(135deg,#6b46c1,#805ad5)}
.lecture-card:nth-child(4) .card-banner{background:linear-gradient(135deg,#c05621,#dd6b20)}
.lecture-card .card-body{padding:20px 22px;flex:1;display:flex;flex-direction:column}
.lecture-card .card-body h3{font-size:1.1rem;color:#1a365d;margin-bottom:6px}
.lecture-card .card-body .card-time{font-size:.82rem;color:#a0aec0;margin-bottom:10px}
.lecture-card .card-body .card-desc{font-size:.85rem;color:#4a5568;line-height:1.6;flex:1}
.lecture-card .card-body .card-arrow{margin-top:14px;align-self:flex-end;width:36px;height:36px;border-radius:50%;background:#edf2f7;display:flex;align-items:center;justify-content:center;font-size:1.1rem;transition:background .2s}
.lecture-card:hover .card-arrow{background:#1a365d;color:#fff}

/* ========== LECTURE PAGE LAYOUT ========== */
.lecture-page{padding-top:64px;min-height:100vh;display:flex;flex-direction:column}
.lecture-header{text-align:center;padding:20px 24px 8px;background:#fff;border-bottom:1px solid #e2e8f0}
.lecture-header h2{font-size:1.25rem;color:#1a365d;font-weight:600}
.lecture-header .lecture-meta{font-size:.82rem;color:#a0aec0;margin-top:4px}

/* Slide container */
.slide-wrapper{flex:1;display:flex;align-items:center;justify-content:center;padding:32px 24px}
.slide-card{background:#fff;border-radius:20px;box-shadow:0 4px 32px rgba(0,0,0,.08);width:100%;max-width:960px;min-height:440px;padding:44px 52px;position:relative;overflow:hidden;transition:opacity .35s ease,transform .35s ease}
.slide-card.fade-out{opacity:0;transform:translateY(12px)}
.slide-card.fade-in{opacity:1;transform:translateY(0)}
.slide-number{position:absolute;top:20px;right:28px;font-size:.82rem;color:#cbd5e0;font-weight:500}
.slide-title{font-size:1.55rem;color:#1a365d;font-weight:700;margin-bottom:28px;padding-bottom:14px;border-bottom:3px solid #c49340;display:inline-block}
.slide-content{font-size:1rem;color:#2d3748;line-height:1.85}
.slide-content ul,.slide-content ol{padding-left:24px;margin:10px 0}
.slide-content li{margin-bottom:8px}
.slide-content strong,.slide-content b{color:#1a365d}
.slide-content .highlight{background:linear-gradient(180deg,transparent 60%,#fefcbf 60%);padding:0 4px}
.slide-content .tag{display:inline-block;padding:2px 10px;border-radius:12px;font-size:.78rem;font-weight:600;margin-right:6px}
.tag-blue{background:#bee3f8;color:#2b6cb0}
.tag-red{background:#fed7d7;color:#c53030}
.tag-green{background:#c6f6d5;color:#276749}
.tag-purple{background:#e9d8fd;color:#6b46c1}
.tag-orange{background:#feebc8;color:#c05621}
.slide-content table{width:100%;border-collapse:collapse;margin:16px 0;font-size:.9rem}
.slide-content th,.slide-content td{border:1px solid #e2e8f0;padding:10px 14px;text-align:left}
.slide-content th{background:#edf2f7;color:#1a365d;font-weight:600}
.slide-content .quote-block{border-left:4px solid #c49340;padding:12px 20px;margin:16px 0;background:#fffbeb;border-radius:0 8px 8px 0;font-style:italic;color:#744210}
.slide-content .danger-box{border-left:4px solid #e53e3e;padding:12px 20px;margin:16px 0;background:#fff5f5;border-radius:0 8px 8px 0}
.slide-content .info-box{border-left:4px solid #3182ce;padding:12px 20px;margin:16px 0;background:#ebf8ff;border-radius:0 8px 8px 0}
.slide-content .grid-2{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin:16px 0}
.slide-content .grid-3{display:grid;grid-template-columns:1fr 1fr 1fr;gap:16px;margin:16px 0}
.slide-content .card-mini{background:#f7fafc;border-radius:10px;padding:16px;border:1px solid #e2e8f0}

/* ========== NAVIGATION ========== */
.nav-bar{display:flex;align-items:center;justify-content:center;gap:16px;padding:16px 24px 28px;background:transparent}
.nav-btn{width:44px;height:44px;border-radius:50%;border:2px solid #cbd5e0;background:#fff;color:#4a5568;font-size:1.2rem;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all .2s;text-decoration:none}
.nav-btn:hover:not(:disabled):not(.nav-disabled){border-color:#1a365d;color:#1a365d;background:#ebf8ff}
.nav-btn:disabled,.nav-btn.nav-disabled{opacity:.3;cursor:not-allowed;pointer-events:none}
.nav-info{font-size:.85rem;color:#718096;min-width:60px;text-align:center}

/* Dot indicators */
.dots-bar{display:flex;align-items:center;justify-content:center;gap:6px;flex-wrap:wrap;max-width:500px}
.dot{width:8px;height:8px;border-radius:50%;background:#cbd5e0;cursor:pointer;transition:all .2s}
.dot.active{background:#1a365d;width:24px;border-radius:4px}
.dot:hover:not(.active){background:#a0aec0}

/* Keyboard hint */
.kbd-hint{text-align:center;font-size:.72rem;color:#a0aec0;padding:2px 0 6px}
.kbd-hint kbd{display:inline-block;padding:1px 7px;border-radius:4px;border:1px solid #cbd5e0;background:#edf2f7;font-family:monospace;font-size:.72rem;margin:0 2px}

/* Back to home link */
.back-home{display:inline-flex;align-items:center;gap:6px;font-size:.82rem;color:#4a5568;text-decoration:none;padding:8px 16px;border-radius:8px;margin:8px 24px;transition:background .2s}
.back-home:hover{background:#edf2f7;color:#1a365d}

/* Breadcrumb */
.breadcrumb{padding:70px 24px 0;font-size:.82rem;color:#a0aec0}
.breadcrumb a{color:#4a5568;text-decoration:none}
.breadcrumb a:hover{color:#1a365d}

/* ========== LECTURE OVERVIEW (TOC) PAGE ========== */
.toc-page{max-width:780px;margin:0 auto;padding:80px 24px 60px}
.toc-page h2{font-size:1.3rem;color:#1a365d;margin-bottom:6px}
.toc-page .toc-subtitle{font-size:.85rem;color:#a0aec0;margin-bottom:28px}
.toc-list{display:flex;flex-direction:column;gap:8px}
.toc-item{display:flex;align-items:center;gap:16px;background:#fff;border-radius:12px;padding:14px 20px;box-shadow:0 1px 6px rgba(0,0,0,.04);text-decoration:none;color:inherit;transition:transform .15s,box-shadow .15s}
.toc-item:hover{transform:translateX(4px);box-shadow:0 2px 12px rgba(0,0,0,.08)}
.toc-item .toc-num{font-weight:700;color:#c49340;font-size:.95rem;min-width:44px;text-align:center}
.toc-item .toc-title{font-size:.9rem;color:#2d3748;flex:1}
.toc-item .toc-arrow{color:#cbd5e0;font-size:.85rem}

.toc-section{margin:24px 0 8px;padding:8px 14px;background:linear-gradient(135deg,#1a365d,#2b6cb0);color:#fff;border-radius:8px;font-size:1.05rem;font-weight:700;letter-spacing:.5px}
.toc-section:first-of-type{margin-top:12px}
.toc-section em{font-style:normal;font-weight:400;opacity:.85;font-size:.9rem;margin-left:6px}

/* Progress bar for lecture overview */
.toc-progress{display:flex;align-items:center;gap:8px;margin-bottom:24px;color:#718096;font-size:.82rem}
.toc-progress .progress-bar{flex:1;height:4px;background:#e2e8f0;border-radius:2px;overflow:hidden}
.toc-progress .progress-fill{height:100%;background:linear-gradient(90deg,#c49340,#ecc94b);border-radius:2px;transition:width .3s}

/* ========== SINGLE SLIDE PAGE — PPT FULLSCREEN ========== */
body.slide-page{height:100vh;overflow:hidden;background:#1a202c}

.single-slide-page{height:100vh;display:flex;flex-direction:column;overflow:hidden}
/* 面包屑：做成明显可见的胶囊（原为 30% 透明度小字，几乎看不见） */
.slide-breadcrumb{position:absolute;top:56px;right:18px;z-index:10;display:flex;align-items:center;gap:6px;
  font-size:.78rem;color:rgba(255,255,255,.92);background:rgba(10,18,32,.55);padding:4px 12px;border-radius:14px;
  box-shadow:0 2px 8px rgba(0,0,0,.25)}
.slide-breadcrumb a{color:#bee3f8;text-decoration:none}
.slide-breadcrumb a:hover{color:#fff;text-decoration:underline}
.slide-breadcrumb .sep{opacity:.45}
.slide-breadcrumb .cur{color:#fff;font-weight:600}

/* 幻灯片自适应基准单位：同时受视口宽度(1.75vw)与高度(3.05vh)约束，
   任何分辨率/窗口尺寸下都不会超出卡片而被裁切（原为固定 2.1rem 超大字号） */
:root{--su:min(2vw,3.05vh)}

.single-slide-wrapper{flex:1;display:flex;align-items:stretch;justify-content:center;width:100%;padding:clamp(34px,5vh,50px) clamp(4px,1vw,12px) 0;min-height:0;min-width:0;overflow:hidden}
.single-slide-wrapper .slide-card{width:100%;max-width:min(1920px,100%);max-height:calc(100vh - 50px - 36px);padding:clamp(8px,1.1vw,20px) clamp(14px,2.9vw,56px) clamp(6px,.8vw,14px);display:flex;flex-direction:column;overflow:hidden;min-height:0;min-width:0;border-radius:4px;box-shadow:0 4px 24px rgba(0,0,0,.4)}
.single-slide-wrapper .slide-card .slide-number{top:12px;right:20px;font-size:clamp(.6rem,.85vw,1rem);color:#cbd5e0}
.single-slide-wrapper .slide-card .slide-title{font-size:clamp(1.1rem,calc(var(--su) * 1.33),2.8rem);margin-bottom:.4em;padding-bottom:8px;flex-shrink:0}
.single-slide-wrapper .slide-card .slide-content{flex:1;overflow:auto;overscroll-behavior:contain;scrollbar-width:thin;font-size:clamp(.8rem,var(--su),2.1rem);line-height:1.6;min-height:0;min-width:0;padding-right:4px}
.single-slide-wrapper .slide-card .slide-content p{margin-bottom:.5em}
.single-slide-wrapper .slide-card .slide-content ul,.single-slide-wrapper .slide-card .slide-content ol{margin:6px 0;padding-left:clamp(16px,1.5vw,28px)}
.single-slide-wrapper .slide-card .slide-content li{margin-bottom:.2em}
.single-slide-wrapper .slide-card .slide-content table{margin:8px 0;font-size:clamp(.68rem,calc(var(--su) * .83),1.75rem)}
.single-slide-wrapper .slide-card .slide-content th,.single-slide-wrapper .slide-card .slide-content td{padding:clamp(4px,.55vw,10px) clamp(6px,.75vw,14px);word-break:break-word}
.single-slide-wrapper .slide-card .slide-content th{font-size:clamp(.68rem,calc(var(--su) * .83),1.75rem)}
.single-slide-wrapper .slide-card .slide-content .quote-block,.single-slide-wrapper .slide-card .slide-content .danger-box,.single-slide-wrapper .slide-card .slide-content .info-box{padding:clamp(6px,.7vw,12px) clamp(10px,1.05vw,20px);margin:.4em 0;font-size:clamp(.74rem,calc(var(--su) * .88),1.85rem)}
.single-slide-wrapper .slide-card .slide-content .grid-2{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(240px,100%),1fr));gap:clamp(8px,.85vw,16px);margin:8px 0}
.single-slide-wrapper .slide-card .slide-content .grid-3{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(190px,100%),1fr));gap:clamp(6px,.65vw,12px);margin:8px 0}
.single-slide-wrapper .slide-card .slide-content .grid-2>*,.single-slide-wrapper .slide-card .slide-content .grid-3>*{min-width:0}
.single-slide-wrapper .slide-card .slide-content .card-mini{padding:clamp(8px,.85vw,14px);font-size:clamp(.7rem,calc(var(--su) * .81),1.7rem);line-height:1.55;min-width:0}
.single-slide-wrapper .slide-card .slide-content .card-mini h3{font-size:clamp(.76rem,calc(var(--su) * .9),1.9rem)}
.single-slide-wrapper .slide-card .slide-content .tag{font-size:clamp(.58rem,calc(var(--su) * .64),1.35rem);padding:.15em .6em;border-radius:14px}
.single-slide-wrapper .slide-card .slide-content .highlight{padding:0 4px}
.single-slide-wrapper .slide-card .slide-content h1{font-size:clamp(1.25rem,calc(var(--su) * 1.52),3.2rem)}
.single-slide-wrapper .slide-card .slide-content h2{font-size:clamp(1rem,calc(var(--su) * 1.14),2.4rem)}
.single-slide-wrapper .slide-card .slide-content h3{font-size:clamp(.92rem,calc(var(--su) * 1.05),2.2rem)}
.single-slide-wrapper .slide-card .slide-content img{max-width:100%;height:auto}
.single-slide-wrapper .slide-card .slide-content table .inline-logo{height:1.6em;vertical-align:middle;margin-right:6px}

.single-nav-bar{flex-shrink:0;display:flex;align-items:center;justify-content:center;gap:16px;padding:2px 24px 2px}
.single-nav-bar .nav-btn{width:36px;height:36px;font-size:1rem}
.single-nav-bar .nav-label{font-size:.7rem;color:rgba(255,255,255,.35);max-width:110px;text-align:center;line-height:1.2}
.single-nav-bar .nav-label.prev-label{text-align:right}
.single-nav-bar .nav-label.next-label{text-align:left}
.single-nav-bar .nav-info{color:rgba(255,255,255,.45);font-size:.8rem}
body.slide-page .kbd-hint{color:rgba(255,255,255,.25);font-size:.65rem;padding:1px 0 2px}
body.slide-page .kbd-hint kbd{border-color:rgba(255,255,255,.1);background:rgba(255,255,255,.06);color:rgba(255,255,255,.3);font-size:.65rem}
body.slide-page .nav-btn{border-color:rgba(255,255,255,.2);background:rgba(255,255,255,.08);color:rgba(255,255,255,.5)}
body.slide-page .nav-btn:hover:not(.nav-disabled){border-color:rgba(255,255,255,.4);background:rgba(255,255,255,.15);color:#fff}

/* ========== INLINE LOGOS ========== */
.slide-hero-logo{display:flex;align-items:center;gap:18px;margin-bottom:10px}
.slide-hero-logo img{height:64px;width:auto;object-fit:contain}
.logo-row{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.inline-logo{height:40px;width:auto;object-fit:contain;vertical-align:middle;margin-right:2px;border-radius:4px}
.card-mini .inline-logo{height:28px}
.slide-content table .inline-logo{height:32px;vertical-align:middle;margin-right:6px}

/* ========== LECTURE CARDS ON HOME PAGE (overview link) ========== */
.lecture-overview-link{display:inline-flex;align-items:center;gap:6px;font-size:.82rem;color:#3182ce;text-decoration:none;margin-top:8px;padding:4px 0}
.lecture-overview-link:hover{text-decoration:underline}

/* ========== RESPONSIVE ========== */
@media(max-width:768px){
  .slide-card{padding:28px 22px;min-height:auto;border-radius:12px}
  .slide-title{font-size:1.2rem}
  .slide-content{font-size:.9rem}
  .slide-content .grid-2,.slide-content .grid-3{grid-template-columns:1fr}
  .lecture-cards{grid-template-columns:1fr}
  .home-hero h1{font-size:1.4rem}
  .logo-bar{padding:10px 16px}
  .logo-bar img{height:28px}
  .single-nav-bar .nav-label{display:none}
  .toc-page{padding:70px 16px 40px}
  .single-slide-wrapper{padding:44px 2px 0}
  .single-slide-wrapper .slide-card{padding:10px 12px 6px;max-height:calc(100vh - 44px - 30px);border-radius:4px}
}

/* Print styles */
@media print{
  .nav-bar,.dots-bar,.kbd-hint,.back-home,.logo-bar,.single-nav-bar,.breadcrumb,.slide-breadcrumb{display:none!important}
  .lecture-page{padding-top:0}
  .slide-wrapper{padding:0}
  .slide-card{box-shadow:none;border-radius:0;page-break-after:always;min-height:auto}
  .single-slide-page{padding-top:0}
  .single-slide-wrapper{padding:0}
}
/* ========== QUIZ INTERACTIVE ========== */
.quiz{margin:10px 0}
.quiz-opt{display:block;width:100%;text-align:left;margin:8px 0;padding:12px 20px;border:2px solid #cbd5e0;border-radius:12px;background:#ffffff;font:inherit;color:inherit;cursor:pointer;transition:all .15s}
.quiz-opt:hover{border-color:#3182ce;background:#ebf8ff}
.quiz-opt.correct{border-color:#38a169;background:#c6f6d5;color:#22543d}
.quiz-opt.wrong{border-color:#e53e3e;background:#fed7d7;color:#742a2a}
.quiz-opt:disabled{cursor:default;opacity:.9}
.quiz-feedback{display:none;margin-top:12px;padding:12px 18px;border-radius:10px;line-height:1.7}
.quiz-feedback.show{display:block}
.quiz-feedback.ok{background:#f0fff4;border-left:5px solid #38a169;color:#22543d}
.quiz-feedback.no{background:#fff5f5;border-left:5px solid #e53e3e;color:#742a2a}
.quiz-btn{display:inline-block;margin:10px 8px 0 0;padding:10px 22px;border:none;border-radius:10px;background:#2b6cb0;color:#fff;font:inherit;font-size:.85em;cursor:pointer;transition:background .15s}
.quiz-btn:hover{background:#2c5282}
.quiz-answered .quiz-opt:not(.correct){opacity:.45}
.single-slide-wrapper .slide-card .slide-content .quiz-opt{font-size:clamp(.7rem,calc(var(--su) * .95),2rem);padding:clamp(7px,1vw,18px) clamp(12px,1.6vw,30px);margin:clamp(5px,.6vw,12px) 0;line-height:1.5}
.single-slide-wrapper .slide-card .slide-content .quiz-btn{font-size:clamp(.65rem,calc(var(--su) * .81),1.7rem);padding:clamp(6px,.75vw,14px) clamp(14px,1.8vw,34px)}
.single-slide-wrapper .slide-card .slide-content .quiz-feedback{font-size:clamp(.72rem,calc(var(--su) * .86),1.8rem)}