@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@500;600;700;800&family=Inter:wght@300;400;500;600;700&display=swap');:root{--white:#ffffff;--bg:#fbfaff;--stone-100:#f4f1ff;--stone-200:#e9e5f9;--stone-400:#b3aed1;--stone-600:#847fa3;--stone-900:#181433;--ink:#181433;--ink-mid:#4a4570;--ink-soft:#544e78;--ink-faint:#6d6494;--border:#e9e5f9;--border-lt:#f2effb;--serif:'Poppins',-apple-system,sans-serif;--sans:'Inter',-apple-system,'Helvetica Neue',sans-serif;--primary:#5B3DF5;--primary-dark:#4527D6;--primary-tint:#ece7fe;--orange:#FF7A3D;--orange-dark:#E85E1F;--orange-tint:#ffeee3;--green:#1FAA6E;--green-tint:#e4f8ee;--nav-h:58px;--max:1100px;--pad:64px;--r-sm:8px;--r-md:14px;--r-lg:20px;--r-xl:24px;--r-2xl:32px;--r-pill:999px;--shadow-xs:0 1px 2px rgba(24,20,51,0.05);--shadow-sm:0 2px 8px rgba(24,20,51,0.07);--shadow-md:0 6px 24px rgba(24,20,51,0.09);--shadow-lg:0 16px 48px rgba(24,20,51,0.11);--shadow-primary:0 10px 26px rgba(91,61,245,0.28);--shadow-orange:0 8px 22px rgba(255,122,61,0.32);--ease:cubic-bezier(0.22,1,0.36,1);--spring:cubic-bezier(0.34,1.56,0.64,1)}*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}html{-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;scroll-behavior:smooth;overflow-x:hidden}body{font-family:var(--sans);color:var(--ink);background:var(--white);line-height:1.6;overflow-x:hidden;font-size:16px}a{text-decoration:none;color:inherit}ul{list-style:none}svg{display:block;flex-shrink:0}button{font-family:var(--sans);cursor:pointer;border:none;background:none}input,select,textarea{font-family:var(--sans)}img{display:block;max-width:100%}.container{max-width:var(--max);margin:0 auto;padding:0 28px}.content-wrap{max-width:820px}.section{padding:var(--pad) 0}.section-tight{padding:36px 0}.section-alt{background:var(--stone-100)}.fade-in{opacity:0;transform:translateY(18px);transition:opacity 0.55s var(--ease),transform 0.55s var(--ease)}.fade-in.visible{opacity:1;transform:translateY(0)}.skip-link{position:absolute;top:-48px;left:8px;z-index:200;background:var(--ink);color:#fff;padding:10px 18px;border-radius:var(--r-md);font-size:14px;font-weight:600;text-decoration:none;transition:top 0.15s}.skip-link:focus{top:8px}.header{position:fixed;top:0;left:0;right:0;z-index:100;height:var(--nav-h);background:rgba(251,250,255,0.9);backdrop-filter:saturate(180%) blur(20px);-webkit-backdrop-filter:saturate(180%) blur(20px);border-bottom:1px solid transparent;transition:border-color 0.3s,background 0.3s,box-shadow 0.3s}.header.scrolled{background:rgba(251,250,255,0.98);border-bottom-color:var(--border-lt);box-shadow:var(--shadow-xs)}.header-inner{max-width:var(--max);margin:0 auto;padding:0 28px;height:100%;display:flex;align-items:center;gap:1.5rem}.logo{display:flex;align-items:center;gap:9px;flex-shrink:0;user-select:none}.logo-img{width:36px;height:36px;object-fit:contain;padding:2px}.logo-text{display:block;font-family:var(--serif);font-size:19px;font-weight:800;color:var(--ink)}.nav{display:flex;flex:1;gap:4px}.nav-link{font-size:14px;font-weight:600;color:var(--ink-soft);padding:8px 15px;border-radius:var(--r-pill);transition:color 0.15s,background 0.15s}.nav-link:hover{color:var(--primary);background:var(--primary-tint)}.header-right{display:flex;align-items:center;gap:14px;flex-shrink:0}.search-wrap{position:relative}.search-btn{display:flex;align-items:center;justify-content:center;width:36px;height:36px;border-radius:var(--r-pill);color:var(--ink-soft);background:var(--stone-100);transition:background 0.15s,color 0.15s}.search-btn:hover{background:var(--primary-tint);color:var(--primary)}.search-panel{position:absolute;top:calc(100% + 10px);right:0;width:320px;background:var(--white);border:1px solid var(--border);border-radius:var(--r-lg);box-shadow:var(--shadow-lg);overflow:hidden;opacity:0;pointer-events:none;transform:translateY(-6px) scale(0.98);transform-origin:top right;transition:opacity 0.2s var(--ease),transform 0.2s var(--ease)}.search-panel.open{opacity:1;pointer-events:auto;transform:translateY(0) scale(1)}.search-input{width:100%;padding:13px 16px;font-size:14px;border:none;outline:none;border-bottom:1px solid var(--border-lt);color:var(--ink);background:transparent}.search-input:focus-visible{border-bottom-color:var(--primary);box-shadow:0 1px 0 0 var(--primary)}.search-input::placeholder{color:var(--ink-faint)}.search-results{display:none}.search-results.active{display:block}.sr-item{display:flex;flex-direction:column;gap:2px;padding:11px 16px;border-bottom:1px solid var(--border-lt);cursor:pointer;transition:background 0.15s}.sr-item:last-child{border-bottom:none}.sr-item:hover{background:var(--stone-100)}.sr-title{font-size:13.5px;font-weight:500;color:var(--ink)}.sr-meta{font-size:11.5px;color:var(--ink-faint)}.sr-empty{padding:16px;font-size:13px;color:var(--ink-soft)}.coffee-btn{font-size:13.5px;font-weight:700;padding:9px 18px;background:linear-gradient(135deg,var(--primary),var(--primary-dark));color:#fff;border-radius:var(--r-pill);transition:all 0.18s;white-space:nowrap;box-shadow:var(--shadow-primary)}.coffee-btn:hover{transform:translateY(-2px)}.burger{display:none;flex-direction:column;gap:5.5px;padding:6px;margin-left:auto}.burger span{display:block;width:20px;height:1.2px;background:var(--ink);border-radius:2px;transition:all 0.25s var(--ease);transform-origin:center}.burger.open span:nth-child(1){transform:translateY(3.35px) rotate(45deg)}.burger.open span:nth-child(2){transform:translateY(-3.35px) rotate(-45deg)}.mobile-menu{display:none;position:absolute;top:var(--nav-h);left:0;right:0;background:rgba(255,255,255,0.98);backdrop-filter:blur(20px);border-bottom:1px solid var(--border-lt);padding:10px 0 20px;box-shadow:var(--shadow-md)}.mobile-menu.open{display:block}.mobile-link{display:block;padding:12px 28px;font-size:16px;color:var(--ink-mid);transition:color 0.15s}.mobile-link:hover{color:var(--ink)}.mobile-search{padding:12px 28px 4px}.mobile-search-input{width:100%;padding:10px 14px;font-size:14px;border:1px solid var(--border);border-radius:var(--r-md);outline:none;color:var(--ink);background:var(--stone-100)}.mobile-search-input:focus-visible{border-color:var(--primary);box-shadow:0 0 0 2px var(--primary-tint)}.mobile-search-input::placeholder{color:var(--ink-faint)}.mobile-coffee{display:block;margin:12px 28px 0;padding:10px 16px;background:linear-gradient(135deg,var(--primary),var(--primary-dark));color:#fff;border-radius:var(--r-pill);font-size:14px;font-weight:500;text-align:center}.btn-primary{display:inline-flex;align-items:center;padding:13px 30px;background:var(--ink);color:var(--white);font-size:15px;font-weight:500;border-radius:var(--r-pill);transition:all 0.2s;letter-spacing:0.1px;border:none;cursor:pointer;font-family:var(--sans);text-decoration:none}.btn-primary:hover{background:var(--ink-mid);transform:translateY(-1px);box-shadow:var(--shadow-md)}.btn-outline{display:inline-flex;align-items:center;padding:13px 28px;background:transparent;color:var(--ink-mid);font-size:15px;font-weight:400;border-radius:var(--r-pill);border:1px solid var(--stone-200);transition:all 0.2s}.btn-outline:hover{background:var(--stone-100);border-color:var(--stone-400);color:var(--ink)}.ad-slot{display:flex;align-items:center;justify-content:center;background:var(--stone-100);border-top:1px solid var(--border-lt);border-bottom:1px solid var(--border-lt)}.ad-label{font-size:10px;font-weight:500;letter-spacing:1px;text-transform:uppercase;color:var(--ink-faint);padding:5px 14px;border:1px solid var(--border);border-radius:var(--r-pill);background:var(--white)}.ad-banner{min-height:90px;padding:12px 28px}.ad-inline{min-height:100px;border-radius:var(--r-xl);border:1px dashed var(--border);margin:24px 0}.ad-inline-seo{min-height:90px;border-radius:var(--r-lg);border:1px dashed var(--border);margin:24px 0}.ad-sidebar{min-height:200px;border-radius:var(--r-lg);border:1px dashed var(--border);width:100%;margin-bottom:14px}.hero,.bh-hero{position:relative;padding:calc(var(--nav-h) + 40px) 0 40px;overflow:hidden}.bh-hero-home{padding:calc(var(--nav-h) + 56px) 0 40px}.bh-blob{position:absolute;border-radius:50%;opacity:0.5;z-index:0;pointer-events:none}.bh-blob1{width:420px;height:420px;background:radial-gradient(circle,var(--primary-tint) 0%,transparent 70%);top:-160px;right:-100px}.bh-blob2{width:360px;height:360px;background:radial-gradient(circle,var(--orange-tint) 0%,transparent 70%);bottom:-180px;left:-120px}.bh-hero .container{position:relative;z-index:1}.bh-eyebrow{display:inline-flex;align-items:center;gap:8px;font-size:13px;font-weight:700;color:var(--primary);background:var(--primary-tint);padding:8px 16px;border-radius:var(--r-pill);margin-bottom:20px}.bh-h1{font-family:var(--serif);font-size:clamp(30px,5vw,46px);font-weight:700;letter-spacing:-0.01em;line-height:1.15;color:var(--ink);max-width:760px}.bh-h1-page{font-size:clamp(26px,4vw,34px)}.bh-h1 .hl{color:var(--primary)}.bh-sub{font-size:16.5px;color:var(--ink-soft);margin-top:14px;max-width:600px;line-height:1.7}.bh-hero-cta{display:flex;gap:12px;margin-top:28px;flex-wrap:wrap}.bh-crumb{display:flex;flex-wrap:wrap;align-items:center;gap:6px;font-size:13px;font-weight:600;color:var(--ink-faint);margin-bottom:16px}.bh-crumb a{color:var(--ink-soft)}.bh-crumb a:hover{color:var(--primary)}.bh-crumb .cur{color:var(--ink-mid)}.bh-crumb .sep{color:var(--border)}.trust-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:26px}.trust-pill{font-size:13px;font-weight:600;color:var(--ink-mid);background:var(--white);border:1px solid var(--border);padding:9px 16px;border-radius:var(--r-pill);box-shadow:var(--shadow-sm)}.section-label{font-size:11px;font-weight:600;letter-spacing:1.8px;text-transform:uppercase;color:var(--ink-faint);margin-bottom:10px}.section-title{font-family:var(--serif);font-size:clamp(24px,3.4vw,30px);font-weight:700;letter-spacing:-0.01em;line-height:1.2;margin-bottom:10px;color:var(--ink)}.section-head{max-width:640px;margin-bottom:32px}.section-eyebrow{font-size:12.5px;font-weight:700;color:var(--primary);text-transform:uppercase;letter-spacing:0.04em;margin-bottom:8px}.section-lede{color:var(--ink-soft);font-size:15px}.hub-intro{font-size:16px;line-height:1.8;color:var(--ink-mid);max-width:780px;margin-bottom:28px;font-weight:300}.hub-intro strong{color:var(--ink);font-weight:600}.class-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:20px;margin-top:0}.class-card{display:block;border-radius:var(--r-lg);background:var(--white);box-shadow:var(--shadow-sm);overflow:hidden;transition:transform 0.18s,box-shadow 0.18s;text-decoration:none}.class-card:hover{transform:translateY(-5px);box-shadow:var(--shadow-md)}.class-card-top{padding:24px 24px 46px;color:#fff;position:relative}.class-card-num{font-family:var(--serif);font-size:36px;font-weight:800}.cc-8 .class-card-top{background:linear-gradient(135deg,var(--c8,#3B6DF5),#5C8DFF)}.cc-9 .class-card-top{background:linear-gradient(135deg,var(--c9,#8B3DF5),#B06BFF)}.cc-10 .class-card-top{background:linear-gradient(135deg,var(--c10,#F53D8B),#FF6BB0)}.class-card-body{padding:18px 22px 22px;margin-top:-26px}.class-card-panel{background:var(--white);border-radius:14px;padding:16px 18px;box-shadow:0 4px 14px rgba(24,20,51,0.08)}.class-card-name{font-size:16px;font-weight:700;color:var(--ink);margin-bottom:4px}.class-card-meta{font-size:12.5px;color:var(--ink-faint);margin-bottom:12px}.class-card-go{font-size:12.5px;font-weight:700;color:var(--primary)}.soon-card{opacity:0.75}.soon-badge{display:inline-block;font-size:11px;font-weight:700;color:var(--orange);background:var(--orange-tint);padding:3px 10px;border-radius:var(--r-pill);margin-bottom:8px}.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}.step{padding:26px 24px;background:var(--white);border:1px solid var(--border-lt);border-radius:var(--r-lg);box-shadow:var(--shadow-xs);transition:transform 0.18s,box-shadow 0.18s}.step:hover{transform:translateY(-3px);box-shadow:var(--shadow-md)}.step-icon{width:44px;height:44px;border-radius:12px;display:flex;align-items:center;justify-content:center;font-size:20px;margin-bottom:14px;background:var(--primary-tint)}.step:nth-child(2) .step-icon{background:var(--orange-tint)}.step:nth-child(3) .step-icon{background:var(--green-tint)}.step h3{font-size:16px;font-weight:600;margin-bottom:6px;color:var(--ink)}.step p{font-size:13.5px;color:var(--ink-soft);font-weight:300;line-height:1.65}.seo-card{background:var(--white);border-radius:var(--r-xl);padding:36px 40px;box-shadow:var(--shadow-sm)}.seo-card h2{font-family:var(--serif);font-size:20px;font-weight:700;margin:1.7em 0 0.7em;padding-left:14px;border-left:4px solid var(--primary);color:var(--ink)}.seo-card h2:first-child{margin-top:0}.seo-card p{font-size:15px;line-height:1.8;color:var(--ink-mid);margin-bottom:1.05em;font-weight:300}.seo-card strong{color:var(--ink);font-weight:600}.seo-card ul.check-list{margin:0.5em 0 1.3em;display:grid;gap:9px;list-style:none;padding:0}.seo-card ul.check-list li{display:flex;gap:9px;font-size:14.5px;color:var(--ink-mid);font-weight:300;padding:0;border:none}.seo-card ul.check-list li::before{content:"";flex-shrink:0;width:18px;height:18px;margin-top:2px;border-radius:6px;background:var(--green-tint);background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12' fill='none'%3E%3Cpath d='M2 6l2.5 2.5L10 3' stroke='%231FAA6E' stroke-width='1.8' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");background-repeat:no-repeat;background-position:center}.faq-item{border-top:1px solid var(--border-lt);padding:16px 0}.faq-item:first-child{border-top:none}.faq-q{font-size:15px;font-weight:600;color:var(--ink);margin-bottom:5px}.faq-a{font-size:14px;color:var(--ink-soft);font-weight:300}.credit-strip{display:flex;align-items:center;gap:14px;background:var(--primary-tint);border-radius:var(--r-lg);padding:16px 20px;margin:1.4em 0}.credit-avatar{width:46px;height:46px;border-radius:50%;background:linear-gradient(135deg,var(--primary),#F5399A);flex-shrink:0;display:flex;align-items:center;justify-content:center;color:#fff;font-family:var(--serif);font-weight:700;font-size:16px}.credit-name{font-size:14px;font-weight:700;color:var(--ink)}.credit-role{font-size:12.5px;color:var(--ink-soft)}.toc-list{display:grid;gap:10px}.toc-row{display:flex;align-items:center;gap:16px;padding:16px 18px;background:var(--white);border-radius:var(--r-md);box-shadow:var(--shadow-xs);transition:transform 0.15s,box-shadow 0.15s;text-decoration:none}.toc-row:hover{transform:translateX(4px);box-shadow:var(--shadow-sm)}.toc-num{font-family:var(--serif);font-weight:700;font-size:14px;color:#fff;width:36px;height:36px;border-radius:11px;display:flex;align-items:center;justify-content:center;flex-shrink:0;background:linear-gradient(135deg,var(--primary),var(--primary-dark))}.toc-body{flex:1;min-width:0}.toc-title{font-size:15px;font-weight:600;color:var(--ink)}.toc-meta{font-size:12.5px;color:var(--ink-faint);margin-top:2px}.toc-arrow{color:var(--ink-faint);flex-shrink:0;transition:transform 0.15s,color 0.15s}.toc-row:hover .toc-arrow{color:var(--primary);transform:translateX(2px)}.page-hero{padding-top:calc(var(--nav-h) + 28px);padding-bottom:28px;background:var(--stone-100);border-bottom:1px solid var(--border-lt)}.page-hero-sm{padding-bottom:22px}.page-title{font-family:var(--serif);font-size:clamp(28px,5vw,50px);font-weight:400;letter-spacing:-2px;line-height:1.06;margin-bottom:10px;color:var(--ink)}.page-sub{font-size:16px;color:var(--ink-soft);font-weight:300;line-height:1.7;max-width:500px}.breadcrumb{display:flex;align-items:center;flex-wrap:wrap;gap:4px;margin-bottom:16px;font-size:13px}.breadcrumb a{color:var(--primary);transition:opacity 0.15s}.breadcrumb a:hover{opacity:0.7}.bc-sep{color:var(--stone-400);font-size:12px}.bc-cur{color:var(--ink-soft)}.subject-block{margin-bottom:40px}.subject-hdr{display:flex;align-items:center;gap:12px;margin-bottom:12px;padding-bottom:12px;border-bottom:1px solid var(--border-lt)}.subject-icon{width:34px;height:34px;display:flex;align-items:center;justify-content:center;border-radius:var(--r-sm);font-size:14px;flex-shrink:0}.subject-name{font-size:15px;font-weight:500;flex:1}.subject-count{font-size:12px;color:var(--ink-faint)}.chapter-list{display:flex;flex-direction:column;gap:1px;background:var(--border-lt);border-radius:var(--r-lg);overflow:hidden;border:1px solid var(--border-lt)}.chapter-row{display:flex;align-items:center;justify-content:space-between;padding:16px 18px;background:var(--white);cursor:pointer;transition:background 0.15s}.chapter-row:hover{background:var(--stone-100)}.chapter-row-left{display:flex;align-items:center;gap:14px}.chapter-icon{width:36px;height:36px;display:flex;align-items:center;justify-content:center;border-radius:var(--r-sm);font-size:14px;flex-shrink:0}.chapter-name{font-size:14.5px;font-weight:500;color:var(--ink)}.chapter-meta{font-size:12px;color:var(--ink-faint);margin-top:2px}.chapter-arrow{color:var(--stone-400);transition:color 0.18s,transform 0.22s var(--spring)}.chapter-row:hover .chapter-arrow{color:var(--primary);transform:translateX(3px)}.topic-list{display:flex;flex-direction:column;gap:1px;background:var(--border-lt);border-radius:var(--r-lg);overflow:hidden;border:1px solid var(--border-lt)}.topic-row{display:flex;align-items:center;justify-content:space-between;padding:16px 18px;background:var(--white);cursor:pointer;transition:background 0.15s;gap:12px}.topic-row:hover{background:var(--stone-100)}.topic-row-left{display:flex;align-items:center;gap:14px}.topic-icon{width:38px;height:38px;display:flex;align-items:center;justify-content:center;border-radius:var(--r-sm);font-size:14px;flex-shrink:0}.topic-title{font-size:14.5px;font-weight:500;color:var(--ink)}.topic-desc{font-size:12px;color:var(--ink-faint);margin-top:2px;font-weight:300}.topic-go{display:flex;align-items:center;gap:5px;font-size:13px;font-weight:500;color:var(--stone-400);white-space:nowrap;flex-shrink:0;transition:color 0.18s,transform 0.22s var(--spring);opacity:0}.topic-row:hover .topic-go{color:var(--primary);transform:translateX(3px);opacity:1}.lesson-grid{display:grid;grid-template-columns:1fr 280px;gap:28px;align-items:start}.lesson-main{min-width:0}.lesson-sidebar{display:flex;flex-direction:column;gap:14px;position:sticky;top:calc(var(--nav-h) + 20px)}.ppt-shell{border-radius:var(--r-2xl);overflow:hidden;border:1px solid var(--border-lt);box-shadow:var(--shadow-md)}.ppt-frame-box{position:relative;background:#0a0a0a;border-radius:var(--r-2xl);overflow:hidden}.ppt-frame{display:block;width:100%;aspect-ratio:16/9;border:none;background:#111}kbd{background:rgba(255,255,255,0.07);border:1px solid rgba(255,255,255,0.12);border-radius:4px;padding:2px 7px;font-size:10px;font-family:'SF Mono',monospace;color:rgba(255,255,255,0.4)}.ppt-actions{display:flex;gap:8px;flex-wrap:wrap}.ppt-btn-outline{display:inline-flex;align-items:center;gap:6px;font-size:13px;font-weight:500;padding:7px 16px;border-radius:var(--r-pill);color:rgba(255,255,255,0.65);border:1px solid rgba(255,255,255,0.12);background:rgba(255,255,255,0.05);transition:all 0.18s;font-family:var(--sans)}.ppt-btn-outline:hover{background:rgba(255,255,255,0.1);color:#fff}.ppt-btn-primary{display:inline-flex;align-items:center;gap:6px;font-size:13px;font-weight:500;padding:7px 16px;border-radius:var(--r-pill);color:#1c1917;background:#fbbf24;border:none;transition:all 0.18s;font-family:var(--sans)}.ppt-btn-primary:hover{background:#f59e0b;transform:translateY(-1px)}.ppt-placeholder{aspect-ratio:16/9;background:var(--stone-100);border:1.5px dashed var(--border);border-radius:var(--r-2xl);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:12px;text-align:center;padding:40px}.ppt-placeholder-icon{font-size:28px;color:var(--stone-400)}.ppt-placeholder-title{font-size:17px;font-weight:500;color:var(--ink-soft)}.ppt-placeholder-sub{font-size:13px;color:var(--ink-faint);font-weight:300;line-height:1.7}.seo-content{margin-top:32px}.seo-content h2{font-family:var(--serif);font-size:20px;font-weight:400;letter-spacing:-0.5px;margin:28px 0 10px;color:var(--ink)}.seo-content h2:first-child{margin-top:0}.seo-content p{font-size:15px;color:var(--ink-soft);line-height:1.8;margin-bottom:16px;font-weight:300}.seo-content strong{font-weight:600;color:var(--ink-mid)}.sidebar-box{background:var(--stone-100);border:1px solid var(--border-lt);border-radius:var(--r-lg);padding:16px}.sidebar-box-title{font-size:11px;font-weight:600;letter-spacing:1.2px;text-transform:uppercase;color:var(--ink-faint);margin-bottom:10px}.more-item{display:flex;justify-content:space-between;align-items:center;padding:9px 10px;font-size:13.5px;color:var(--ink-mid);border-radius:var(--r-sm);font-weight:300;transition:background 0.15s,color 0.15s;cursor:pointer}.more-item:hover{background:var(--white);color:var(--ink)}.promo-box{border-radius:var(--r-lg);overflow:hidden;margin-bottom:14px}.promo-quote{background:linear-gradient(135deg,#1e1b4b 0%,#312e81 100%);padding:22px 18px}.promo-quote-mark{font-family:var(--serif);font-size:48px;color:rgba(255,255,255,0.2);line-height:0.6;margin-bottom:10px}.promo-quote-text{font-size:13.5px;color:rgba(255,255,255,0.85);line-height:1.7;font-weight:300;font-style:italic;margin-bottom:10px}.promo-quote-author{font-size:12px;color:rgba(255,255,255,0.4);font-weight:500}.promo-advertise{background:var(--stone-100);padding:12px 18px;border:1px solid var(--border-lt);border-top:none;border-radius:0 0 var(--r-lg) var(--r-lg)}.promo-advertise-link{font-size:12px;font-weight:600;color:var(--primary);display:block;margin-bottom:3px}.promo-advertise-sub{font-size:11px;color:var(--ink-faint)}.pdf-section{margin-top:24px;border-radius:var(--r-xl);overflow:hidden;border:1px solid var(--border-lt);box-shadow:var(--shadow-md);background:#0f0d1a}.pdf-section::before{content:'';display:block;height:3px;background:linear-gradient(90deg,var(--primary) 0%,var(--primary) 50%,#8B3DF5 100%)}.pdf-section:fullscreen,.pdf-section:-webkit-full-screen,.pdf-section.fake-fullscreen{border-radius:0;display:flex;flex-direction:column;background:#1c1a2e}.pdf-section:fullscreen .pdf-canvas-wrap,.pdf-section:-webkit-full-screen .pdf-canvas-wrap,.pdf-section.fake-fullscreen .pdf-canvas-wrap{flex:1;overflow:hidden;display:flex;align-items:center;justify-content:center;padding:16px}.pdf-bar{display:flex;align-items:center;justify-content:space-between;padding:0 16px;height:48px;background:linear-gradient(135deg,#0f0d1a 0%,#1a1535 100%);border-bottom:0.5px solid rgba(255,255,255,0.07);gap:10px;flex-shrink:0}.pdf-bar-left{display:flex;align-items:center;gap:9px;flex:1;min-width:0;color:rgba(255,255,255,0.5)}.pdf-bar-title{font-size:13px;font-weight:500;color:rgba(255,255,255,0.8);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.pdf-bar-badge{font-size:9px;font-weight:700;letter-spacing:1px;text-transform:uppercase;background:#dc2626;color:#fff;padding:3px 8px;border-radius:var(--r-pill);flex-shrink:0}.pdf-bar-center{display:flex;align-items:center;gap:4px;flex-shrink:0}.pdf-nav-btn{width:32px;height:32px;border-radius:var(--r-sm);display:flex;align-items:center;justify-content:center;background:rgba(255,255,255,0.06);border:0.5px solid rgba(255,255,255,0.1);color:rgba(255,255,255,0.7);cursor:pointer;transition:all 0.18s}.pdf-nav-btn:hover{background:rgba(99,102,241,0.2);border-color:rgba(99,102,241,0.4);color:#a5b4fc;transform:scale(1.08)}.pdf-cur{font-size:13px;font-weight:500;color:rgba(255,255,255,0.9);min-width:20px;text-align:center}.pdf-goto{width:64px;height:28px;background:rgba(255,255,255,0.07);border:0.5px solid rgba(255,255,255,0.15);border-radius:var(--r-sm);color:rgba(255,255,255,0.85);font-size:12px;text-align:center;padding:0 6px;outline:none;margin:0 5px;-moz-appearance:textfield}.pdf-goto::-webkit-outer-spin-button,.pdf-goto::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}.pdf-goto::placeholder{color:rgba(255,255,255,0.2);font-size:11px}.pdf-goto:focus{border-color:rgba(99,102,241,0.5)}.pdf-sep{font-size:12px;color:rgba(255,255,255,0.4);margin-right:4px}.pdf-bar-right{display:flex;align-items:center;gap:4px;flex-shrink:0}.pdf-zoom-btn,.pdf-fs-btn{width:32px;height:32px;border-radius:var(--r-sm);display:flex;align-items:center;justify-content:center;background:rgba(255,255,255,0.06);border:0.5px solid rgba(255,255,255,0.1);color:rgba(255,255,255,0.55);cursor:pointer;transition:all 0.18s}.pdf-zoom-btn:hover{background:rgba(255,255,255,0.12);color:#fff}.pdf-fs-btn{background:rgba(99,102,241,0.2);border-color:rgba(99,102,241,0.3);color:#a5b4fc}.pdf-fs-btn:hover{background:rgba(99,102,241,0.35);color:#fff}.pdf-canvas-wrap{background:#1c1a2e;display:flex;flex-direction:column;align-items:center;justify-content:flex-start;padding:24px 16px;height:520px;position:relative;overflow:auto}.pdf-loading{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:14px;padding:80px 20px;color:rgba(255,255,255,0.3);font-size:13px;font-weight:300;position:absolute;inset:0}.pdf-spinner{width:26px;height:26px;border:2px solid rgba(99,102,241,0.15);border-top-color:#6366f1;border-radius:50%;animation:pdfSpin 0.8s linear infinite}@keyframes pdfSpin{to{transform:rotate(360deg)}}.pdf-error{color:rgba(255,100,100,0.8);font-size:13px;text-align:center;max-width:320px;line-height:1.7}.pdf-canvas{display:none;border-radius:3px;box-shadow:0 2px 8px rgba(0,0,0,0.4),0 16px 48px rgba(0,0,0,0.5);background:#fff;-webkit-user-drag:none;user-select:none;-webkit-user-select:none;-moz-user-select:none}.pdf-anno-layer{pointer-events:none;z-index:10}.pdf-anno-layer a{pointer-events:auto;display:block;border-radius:2px;transition:background 0.15s}.pdf-anno-layer a:hover{background:rgba(99,102,241,0.15)}#eb-video-overlay{position:fixed;inset:0;z-index:9999;display:flex;align-items:center;justify-content:center;opacity:0;transition:opacity 0.28s;pointer-events:none}#eb-video-overlay.open{opacity:1;pointer-events:auto}.voverlay-bd{position:absolute;inset:0;background:rgba(0,0,0,0.85);backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px);cursor:pointer}.voverlay-box{position:relative;z-index:1;width:min(860px,94vw);border-radius:var(--r-xl);overflow:hidden;box-shadow:0 32px 80px rgba(0,0,0,0.6);transform:translateY(20px) scale(0.97);transition:transform 0.3s var(--ease)}#eb-video-overlay.open .voverlay-box{transform:translateY(0) scale(1)}.voverlay-bar{display:flex;align-items:center;justify-content:space-between;padding:12px 18px;background:#0f0d1a}.voverlay-title{font-size:13px;font-weight:500;color:rgba(255,255,255,0.7)}.voverlay-close{width:30px;height:30px;display:flex;align-items:center;justify-content:center;border-radius:var(--r-sm);background:rgba(255,255,255,0.06);border:0.5px solid rgba(255,255,255,0.1);color:rgba(255,255,255,0.6);cursor:pointer;transition:all 0.18s}.voverlay-close:hover{background:rgba(255,50,50,0.2);color:#fff}.voverlay-frame{position:relative;width:100%;aspect-ratio:16/9;background:#000}.voverlay-frame iframe{position:absolute;inset:0;width:100%;height:100%;border:none}.static-content h2{font-family:var(--serif);font-size:22px;font-weight:400;letter-spacing:-0.5px;margin:28px 0 10px;color:var(--ink)}.static-content h2:first-child{margin-top:0}.static-content p{font-size:15px;color:var(--ink-soft);line-height:1.8;margin-bottom:14px;font-weight:300}.static-content ul{margin:0 0 16px 20px;list-style:disc}.static-content ul li{font-size:15px;color:var(--ink-soft);line-height:1.8;margin-bottom:6px;font-weight:300}.static-content a{color:var(--primary);text-decoration:underline;text-underline-offset:2px}.static-content em{font-style:italic;color:var(--ink-faint)}.contact-grid{display:grid;grid-template-columns:1fr 1fr;gap:48px}.contact-info h2,.contact-form-wrap h2{font-family:var(--serif);font-size:22px;font-weight:400;letter-spacing:-0.5px;margin-bottom:14px}.contact-info p{font-size:15px;color:var(--ink-soft);line-height:1.75;margin-bottom:16px;font-weight:300}.contact-item{margin-bottom:20px}.contact-label{font-size:11px;font-weight:600;letter-spacing:1px;text-transform:uppercase;color:var(--ink-faint);display:block;margin-bottom:6px}.contact-info a,.contact-note a{color:var(--primary)}.contact-form{display:flex;flex-direction:column;gap:14px}.form-group{display:flex;flex-direction:column;gap:6px}.form-group label{font-size:13px;font-weight:500;color:var(--ink-mid)}.form-input{padding:10px 14px;font-size:14px;border:1px solid var(--border);border-radius:var(--r-md);outline:none;color:var(--ink);background:var(--white);transition:border-color 0.18s}.form-input:focus{border-color:var(--primary)}.form-textarea{resize:vertical;min-height:120px}.contact-note{font-size:12.5px;color:var(--ink-faint);line-height:1.7}.not-found{padding:120px 28px;text-align:center;display:flex;flex-direction:column;align-items:center;gap:20px;padding-top:calc(var(--nav-h) + 120px)}.not-found h2{font-family:var(--serif);font-size:32px;color:var(--ink)}.not-found p{color:var(--ink-soft)}.footer{background:#14102b;color:rgba(255,255,255,0.65);padding:56px 0 0}.footer-inner{max-width:var(--max);margin:0 auto;padding:0 28px 48px;display:grid;grid-template-columns:220px 1fr;gap:60px;border-bottom:1px solid rgba(255,255,255,0.08)}.footer-brand{}.footer-logo{display:flex;align-items:center;gap:9px;font-family:var(--serif);font-size:18px;font-weight:800;color:#fff;margin-bottom:12px}.footer-logo-img{width:24px;height:24px;object-fit:contain;opacity:0.9}.footer-desc{font-size:13.5px;color:rgba(255,255,255,0.55);font-weight:300;line-height:1.75;margin-bottom:6px}.footer-boards{font-size:12px;color:rgba(255,255,255,0.35);font-weight:300}.footer-cols{display:grid;grid-template-columns:repeat(3,1fr);gap:32px}.footer-col{display:flex;flex-direction:column;gap:10px}.footer-col-title{font-size:11px;font-weight:700;letter-spacing:1.3px;text-transform:uppercase;color:rgba(255,255,255,0.45);margin-bottom:4px}.footer-col a{font-size:13.5px;color:rgba(255,255,255,0.65);font-weight:300;transition:color 0.15s}.footer-col a:hover{color:#fff}.footer-bottom{max-width:var(--max);margin:0 auto;padding:18px 28px;display:flex;justify-content:space-between;font-size:12.5px;color:rgba(255,255,255,0.4);font-weight:300;flex-wrap:wrap;gap:6px}.present-bar{position:fixed;top:0;left:0;right:0;height:52px;background:rgba(6,4,18,0.97);backdrop-filter:blur(24px);-webkit-backdrop-filter:blur(24px);display:flex;align-items:center;justify-content:space-between;padding:0 22px;z-index:100;border-bottom:0.5px solid rgba(255,255,255,0.06);transition:transform 0.4s var(--ease),opacity 0.4s}.present-bar.hidden{transform:translateY(-100%);opacity:0;pointer-events:none}.present-hover-strip{position:fixed;top:0;left:0;right:0;height:8px;z-index:200;cursor:pointer}.present-hover-pill{position:fixed;top:14px;left:50%;transform:translateX(-50%) translateY(-10px);background:rgba(12,8,30,0.95);backdrop-filter:blur(12px);border:0.5px solid rgba(99,102,241,0.28);border-radius:var(--r-pill);padding:8px 22px;font-size:12px;font-weight:500;color:rgba(255,255,255,0.75);z-index:201;pointer-events:none;opacity:0;transition:opacity 0.22s,transform 0.3s var(--spring);white-space:nowrap}.present-hover-pill.show{opacity:1;transform:translateX(-50%) translateY(0)}@media(max-width:960px){:root{--pad:68px}.nav,.header-right .coffee-btn{display:none}.burger{display:flex}.lesson-grid{grid-template-columns:1fr}.lesson-sidebar{position:static}.steps{grid-template-columns:1fr}.steps .step+.step{border-top:1px solid var(--border-lt)}.footer-inner{grid-template-columns:1fr;gap:40px}.contact-grid{grid-template-columns:1fr}}@media(max-width:640px){:root{--pad:52px}.hero-title{letter-spacing:-1.5px}.hero-stats{flex-direction:column;padding:14px 24px;border-radius:var(--r-xl)}.stat-sep{width:40px;height:1px}.stat{padding:8px 0}.class-grid{grid-template-columns:1fr}.footer-cols{grid-template-columns:1fr 1fr}.hero-cta,.bh-hero-cta{flex-direction:column;align-items:stretch}.pdf-bar-title{display:none}.search-panel{position:fixed;top:calc(var(--nav-h) + 8px);left:12px;right:12px;width:auto;transform:translateY(-6px)}.search-panel.open{transform:translateY(0)}.pdf-bar{flex-wrap:wrap;height:auto;padding:8px 12px;row-gap:6px;justify-content:center}}.seo-formula{background:var(--stone-100);border:1px solid var(--border-lt);border-left:3px solid var(--primary);border-radius:var(--r-md);padding:14px 18px;margin:0 0 20px 0;overflow-x:auto}.seo-formula code{font-family:var(--mono,ui-monospace,SFMono-Regular,Menlo,monospace);font-size:14px;color:var(--ink-mid);white-space:pre-wrap;line-height:1.6}.seo-points{margin:0 0 20px 0;padding:0;list-style:none}.seo-points li{font-size:14.5px;color:var(--ink-soft);line-height:1.75;font-weight:300;padding:9px 0 9px 22px;border-bottom:1px solid var(--border-lt);position:relative}.seo-points li:last-child{border-bottom:none}.seo-points li::before{content:"";position:absolute;left:0;top:18px;width:7px;height:7px;border-radius:50%;background:var(--primary);opacity:0.5}.seo-table-wrap{overflow-x:auto;margin:0 0 20px 0;border:1px solid var(--border-lt);border-radius:var(--r-md)}.seo-table{width:100%;border-collapse:collapse;font-size:14px}.seo-table caption{caption-side:top;text-align:left;font-size:13px;color:var(--ink-faint);padding:10px 14px 0;font-weight:300}.seo-table th,.seo-table td{padding:10px 14px;text-align:left;border-bottom:1px solid var(--border-lt);color:var(--ink-soft);font-weight:300;line-height:1.5}.seo-table th{background:var(--stone-100);color:var(--ink-mid);font-weight:600;font-size:13px}.seo-table tr:last-child td{border-bottom:none}.seo-table tbody tr:hover td{background:var(--bg)}.seo-diagram{margin:0 0 20px 0;padding:18px;background:var(--stone-100);border:1px solid var(--border-lt);border-radius:var(--r-md);text-align:center}.seo-diagram svg{max-width:100%;height:auto}.seo-diagram figcaption{margin-top:8px;font-size:12.5px;color:var(--ink-faint);font-weight:300}.seo-diagram svg text.ts{font-size:11px}.author-profile{display:flex;align-items:flex-start;gap:28px;padding:28px;background:var(--bg-alt);border-radius:var(--r-xl);margin-bottom:36px;border:1px solid var(--border-lt)}.author-photo{width:120px;height:120px;border-radius:50%;object-fit:cover;flex-shrink:0;border:3px solid var(--border)}.author-details h2{margin-top:0;margin-bottom:10px}.author-details p{margin:0 0 12px 0;font-size:14.5px;color:var(--ink-soft);line-height:1.7}.author-link{display:inline-flex;align-items:center;gap:6px;font-size:13px;color:var(--primary);text-decoration:none;font-weight:500;border:1px solid #c7d2fe;padding:5px 14px;border-radius:20px;transition:background .15s}.author-link:hover{background:#eef2ff}@media(max-width:600px){.author-profile{flex-direction:column}.author-photo{width:80px;height:80px}}.footer-author-bio{font-size:12px;color:var(--ink-muted,#9ca3af);line-height:1.6;margin-top:10px;max-width:280px}.static-content ul{padding-left:22px;margin:12px 0 20px 0}.static-content ul li{font-size:15px;color:var(--ink-soft);line-height:1.75;margin-bottom:6px}.static-content ul li strong{color:var(--ink)}.ad-slot.ad-sidebar{min-height:250px;width:100%;border-radius:var(--r-lg)}.static-content h2:first-of-type{margin-top:0}.author-bio-inline{display:flex;align-items:center;gap:12px;background:#f8faff;border:1px solid #e2e8f0;border-radius:10px;padding:14px 16px;margin-top:24px}.author-bio-photo{width:56px;height:56px;border-radius:50%;object-fit:cover;flex-shrink:0;border:2px solid #dbeafe}.author-bio-text{font-size:13px;color:#475569;line-height:1.5}.author-bio-text strong{color:#1e293b;display:block;margin-bottom:2px}.author-bio-link{color:var(--primary);text-decoration:none;font-weight:500;font-size:12px}.author-bio-link:hover{text-decoration:underline}.contact-submit-btn{width:100%;margin-top:8px;justify-content:center;font-size:15px;padding:14px 24px}.contact-note{font-size:13px;color:#64748b;margin-top:10px}.contact-note a{color:var(--primary)}.form-group{margin-bottom:16px}.form-group label{display:block;font-size:13px;font-weight:500;color:#374151;margin-bottom:6px}.form-textarea{resize:vertical;min-height:120px}.team-section{margin-top:48px;padding-top:40px;border-top:1px solid var(--border-lt)}.team-heading{margin-bottom:28px}.team-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:24px}.team-card{display:flex;flex-direction:column;align-items:center;text-align:center;background:var(--white);border:1px solid var(--border-lt);border-radius:var(--r-xl);padding:32px 24px;box-shadow:var(--shadow-sm);transition:box-shadow 0.2s}.team-card:hover{box-shadow:var(--shadow-md)}.team-avatar-wrap{position:relative;margin-bottom:18px}.team-avatar{width:120px;height:120px;border-radius:50%;object-fit:cover;border:3px solid var(--border-lt);display:block}.team-avatar-fallback{width:120px;height:120px;border-radius:50%;background:linear-gradient(135deg,var(--primary),#8B3DF5);align-items:center;justify-content:center;font-size:36px;font-weight:700;color:#fff;letter-spacing:1px;margin-bottom:0}.team-name{font-size:18px;font-weight:700;color:var(--ink);margin-bottom:4px}.team-title{font-size:13px;font-weight:600;color:var(--primary);text-transform:uppercase;letter-spacing:0.05em;margin-bottom:12px}.team-bio{font-size:14px;color:var(--ink-mid);line-height:1.65;max-width:340px}@media(max-width:600px){.team-grid{grid-template-columns:1fr}.team-card{padding:24px 16px}}.support-wrap{display:grid;grid-template-columns:1fr 1fr;gap:48px;align-items:start;max-width:900px;margin:0 auto}.support-intro h2{margin-bottom:16px}.support-intro p{color:var(--ink-mid);line-height:1.7;margin-bottom:14px}.support-list{list-style:none;padding:0;margin:20px 0 0}.support-list li{font-size:15px;color:var(--ink-mid);padding:6px 0;border-bottom:1px solid var(--border-lt)}.support-list li:last-child{border-bottom:none}.support-donate-box{background:var(--white);border:1px solid var(--border-lt);border-radius:var(--r-xl);padding:32px 24px;text-align:center;box-shadow:var(--shadow-sm)}.support-qr-wrap{margin-bottom:20px;display:flex;justify-content:center;align-items:center}.support-qr{width:200px;height:200px;border-radius:12px;border:2px solid var(--border-lt);object-fit:contain;background:#fff;display:block;margin:0 auto}.support-upi-label{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.08em;color:var(--ink-faint);margin-bottom:4px}.support-upi-id-wrap{display:inline-flex;align-items:center;background:var(--stone-100);border:1px solid var(--border);border-radius:8px;padding:8px 12px 8px 16px;margin:6px 0 4px;gap:8px}.support-upi-id{font-size:18px;font-weight:700;color:var(--ink);font-family:monospace;word-break:break-all}.upi-copy-btn{display:inline-flex;align-items:center;justify-content:center;background:none;border:none;cursor:pointer;padding:2px;color:var(--ink-faint);transition:color 0.15s;flex-shrink:0}.upi-copy-btn:hover{color:var(--ink)}.support-upi-name{font-size:14px;font-weight:600;color:var(--primary);margin-bottom:12px}.support-upi-hint{font-size:13px;color:var(--ink-faint);line-height:1.6}@media(max-width:720px){.support-wrap{grid-template-columns:1fr;gap:32px}.support-donate-box{padding:24px 16px}}.promo-img-link{display:block;line-height:0}.promo-img{width:100%;height:auto;border-radius:var(--r-lg) var(--r-lg) 0 0;object-fit:cover;transition:opacity 0.2s}.promo-img-link:hover .promo-img{opacity:0.9}.promo-img[src=""]{display:none}.promo-img:not([src]){display:none}.footer-social{display:flex;gap:10px;margin-top:16px;flex-wrap:wrap}.social-bar{display:flex;gap:10px;flex-wrap:wrap;margin-top:12px}.social-link{display:inline-flex;align-items:center;justify-content:center;width:36px;height:36px;border-radius:50%;background:var(--stone-100);color:var(--ink-mid);transition:background 0.18s,color 0.18s,transform 0.18s;text-decoration:none;flex-shrink:0}.social-link:hover{transform:translateY(-2px)}.social-link.social-x:hover{background:#000;color:#fff}.social-link.social-instagram:hover{background:radial-gradient(circle at 30% 107%,#fdf497 0%,#fdf497 5%,#fd5949 45%,#d6249f 60%,#285aeb 90%);color:#fff}.social-link.social-youtube:hover{background:#ff0000;color:#fff}.social-link.social-facebook:hover{background:#1877f2;color:#fff}.footer .social-link{background:rgba(255,255,255,0.08);color:rgba(255,255,255,0.6)}.footer .social-link:hover{background:rgba(255,255,255,0.18);color:#fff}.contact-social{margin-top:8px}.about-social{margin-top:24px;padding-top:24px;border-top:1px solid var(--border-lt)}.seo-content h3{font-family:var(--serif);font-size:17px;font-weight:400;letter-spacing:-0.3px;margin:24px 0 8px;color:var(--ink)}.seo-content ul{margin:0 0 16px 0;padding:0;list-style:none}.seo-content ul li{font-size:15px;color:var(--ink-soft);line-height:1.75;font-weight:300;padding:7px 0 7px 20px;border-bottom:1px solid var(--border-lt);position:relative}.seo-content ul li:last-child{border-bottom:none}.seo-content ul li::before{content:"";position:absolute;left:0;top:16px;width:7px;height:7px;border-radius:50%;background:var(--primary);opacity:0.5}.seo-content ol{margin:0 0 16px 0;padding:0 0 0 20px}.seo-content ol li{font-size:15px;color:var(--ink-soft);line-height:1.75;font-weight:300;margin-bottom:8px}#cookie-banner{position:fixed;bottom:0;left:0;right:0;z-index:9999;background:#1a1a2e;color:#e8e8f0;padding:16px 24px;display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap;box-shadow:0 -2px 12px rgba(0,0,0,0.25);font-size:14px;line-height:1.5}#cookie-banner.hidden{display:none}#cookie-banner p{margin:0;flex:1;min-width:220px;color:#c8c8dc}#cookie-banner p a{color:#a5b4fc;text-decoration:underline}#cookie-banner p a:hover{color:#c7d2fe}.cookie-btns{display:flex;gap:10px;flex-shrink:0}.cookie-btns button{padding:9px 20px;border-radius:6px;font-size:13px;font-weight:500;cursor:pointer;border:none;transition:opacity 0.15s}#cookie-accept{background:#4f46e5;color:#fff}#cookie-accept:hover{opacity:0.88}#cookie-decline{background:transparent;color:#a0a0b8;border:1px solid #3a3a5c!important}#cookie-decline:hover{background:#2a2a40;color:#c8c8dc}@media(max-width:560px){#cookie-banner{flex-direction:column;align-items:flex-start}.cookie-btns{width:100%}.cookie-btns button{flex:1}}#back-to-top{position:fixed;bottom:calc(env(safe-area-inset-bottom,0px) + 24px);right:calc(env(safe-area-inset-right,0px) + 20px);z-index:90;width:46px;height:46px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--primary-dark));color:#fff;border:none;display:flex;align-items:center;justify-content:center;box-shadow:var(--shadow-primary);cursor:pointer;opacity:0;pointer-events:none;transform:translateY(12px);transition:opacity 0.25s var(--ease),transform 0.25s var(--ease),bottom 0.2s var(--ease)}#back-to-top.show{opacity:1;pointer-events:auto;transform:translateY(0)}#back-to-top:hover{filter:brightness(1.08)}#back-to-top:focus-visible{outline:2px solid var(--primary);outline-offset:3px}@media(max-width:640px){#back-to-top{width:42px;height:42px}}.chapter-num-badge,.topic-num-badge{font-family:var(--serif);font-weight:700;color:#fff;display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,var(--primary),var(--primary-dark));border-radius:12px}.chapter-num-badge{width:38px;height:38px;font-size:14px}.topic-num-badge{width:36px;height:36px;font-size:14px}.lesson-container{max-width:900px;margin:0 auto}.lesson-head{padding-top:calc(var(--nav-h) + 28px);padding-bottom:8px}.lesson-badges{display:flex;gap:8px;margin-bottom:14px;flex-wrap:wrap}.badge{font-size:12px;font-weight:700;padding:5px 13px;border-radius:var(--r-pill)}.badge-blue{background:var(--primary-tint);color:var(--primary)}.badge-green{background:var(--green-tint);color:var(--green)}.lesson-intro{font-size:16px;line-height:1.8;color:var(--ink-soft);font-weight:300;margin-top:14px}.lesson-intro strong{color:var(--ink);font-weight:600}.lesson-body{padding:8px 0 64px}.lesson-more-section{display:flex;gap:16px;flex-wrap:wrap;margin:36px 0}.lesson-more-section .sidebar-box,.lesson-more-section .ad-promo-box{flex:1;min-width:240px}.present-block{margin:28px 0;border-radius:var(--r-xl);overflow:hidden;box-shadow:var(--shadow-md);background:#0d0b1f}.embed-bar{display:flex;align-items:center;justify-content:space-between;padding:10px 12px 10px 18px;background:#181433;gap:10px;flex-wrap:wrap;position:relative;z-index:1}.present-tabs{display:flex;gap:6px}.present-tab{font-family:var(--sans);font-size:12.5px;font-weight:700;color:rgba(255,255,255,0.5);background:transparent;border:none;padding:8px 14px;border-radius:var(--r-pill);cursor:pointer;transition:all 0.15s}.present-tab:hover{color:#fff}.present-tab.active{color:#fff;background:rgba(255,255,255,0.14)}.present-fs-btn{display:flex;align-items:center;gap:7px;font-size:13px;font-weight:700;color:#fff;background:rgba(255,255,255,0.12);padding:8px 14px;border-radius:var(--r-pill);border:none;cursor:pointer;transition:background 0.15s;flex-shrink:0;font-family:var(--sans)}.present-fs-btn:hover{background:rgba(255,255,255,0.22)}.present-frame-wrap{position:relative}.present-frame-wrap:fullscreen,.present-frame-wrap:-webkit-full-screen,.present-frame-wrap.fake-fullscreen{background:#000;overflow:hidden}.present-frame-wrap:fullscreen .present-pane.active,.present-frame-wrap:-webkit-full-screen .present-pane.active,.present-frame-wrap.fake-fullscreen .present-pane.active{width:100%;height:100%}.present-frame-wrap:fullscreen .present-embed,.present-frame-wrap:-webkit-full-screen .present-embed,.present-frame-wrap.fake-fullscreen .present-embed,.present-frame-wrap:fullscreen .present-poster,.present-frame-wrap:-webkit-full-screen .present-poster,.present-frame-wrap.fake-fullscreen .present-poster{width:100%;height:100%;aspect-ratio:auto}.fake-fullscreen{position:fixed!important;top:0!important;left:0!important;right:0!important;bottom:0!important;width:100vw!important;height:100vh!important;height:100dvh!important;z-index:9999;margin:0!important;border-radius:0!important}body.fake-fullscreen-lock{overflow:hidden}.fake-fullscreen-exit{position:fixed;top:calc(env(safe-area-inset-top,0px) + 12px);right:calc(env(safe-area-inset-right,0px) + 12px);z-index:10000;width:40px;height:40px;border-radius:50%;background:rgba(0,0,0,0.65);color:#fff;display:flex;align-items:center;justify-content:center;border:none;cursor:pointer}.present-pane{display:none}.present-pane.active{display:block}.present-poster,.present-embed{aspect-ratio:16/9;width:100%}.present-embed{border:0;display:block;background:#fff}.present-poster{position:relative;display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,var(--primary-tint),var(--orange-tint));cursor:pointer;border:none;padding:0}.present-poster-icon{width:68px;height:68px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--primary-dark));display:flex;align-items:center;justify-content:center;color:#fff;box-shadow:0 8px 24px rgba(0,0,0,0.35),var(--shadow-primary);transition:transform 0.18s}.present-poster:hover .present-poster-icon{transform:scale(1.08)}.present-caption{position:absolute;left:50%;bottom:20px;transform:translateX(-50%);background:rgba(13,11,31,0.6);backdrop-filter:blur(6px);color:#fff;font-family:var(--serif);font-weight:600;font-size:13px;padding:9px 18px;border-radius:var(--r-pill);white-space:nowrap}.present-pane .pdf-section{margin-top:0;border-radius:0;border:none;box-shadow:none;background:transparent}.present-pane .pdf-section::before{display:none}.present-pane .pdf-canvas{box-shadow:0 4px 16px rgba(0,0,0,0.3)}.lesson-nextprev{display:flex;justify-content:space-between;gap:16px;margin-top:44px;flex-wrap:wrap}.np-link{font-size:13px;font-weight:500;color:var(--ink-soft);background:var(--white);border:1px solid var(--border-lt);padding:14px 20px;border-radius:var(--r-md);box-shadow:var(--shadow-xs);transition:transform 0.15s,box-shadow 0.15s;flex:1;min-width:200px}.np-link:hover{transform:translateY(-2px);box-shadow:var(--shadow-sm)}.np-link span{display:block;font-size:14.5px;font-weight:600;color:var(--ink);margin-top:4px}.np-next{text-align:right}.ad-promo-box{background:linear-gradient(135deg,var(--primary-tint),var(--orange-tint));border:1px solid var(--border-lt);border-radius:var(--r-lg);padding:20px;display:flex;flex-direction:column;gap:8px}.ad-promo-label{font-size:11px;font-weight:700;text-transform:uppercase;letter-spacing:0.06em;color:var(--ink-faint)}.ad-promo-title{font-size:15px;font-weight:700;color:var(--ink)}.ad-promo-sub{font-size:12.5px;color:var(--ink-soft);line-height:1.5}.ad-promo-link{font-size:12.5px;font-weight:700;color:var(--primary);margin-top:4px}@media(max-width:720px){.lesson-nextprev{flex-direction:column}.np-next{text-align:left}}@media print{.pdf-section,.present-block,.header,.footer,.lesson-sidebar,#cookie-banner{display:none!important}body::before{content:"EduBadi lesson content is view-only and is not available for printing. Please visit the lesson on edubadi.com.";display:block;padding:40px;font-size:16px;text-align:center}}