:root{--accent: #0071e3;--accent-hover: #0077ed;--accent-light: #147ce5;--bg-primary: #ffffff;--bg-secondary: #f5f5f7;--bg-tertiary: #fbfbfd;--bg-card: #ffffff;--bg-hover: rgba(0, 0, 0, .04);--text-primary: #1d1d1f;--text-secondary: #6e6e73;--text-tertiary: #86868b;--border-color: rgba(0, 0, 0, .08);--border-strong: rgba(0, 0, 0, .12);--shadow-sm: 0 2px 8px rgba(0, 0, 0, .04);--shadow-md: 0 4px 20px rgba(0, 0, 0, .08);--shadow-lg: 0 12px 40px rgba(0, 0, 0, .12);--shadow-card: 0 2px 12px rgba(0, 0, 0, .08);--font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "Helvetica Neue", "PingFang SC", sans-serif;--font-mono: "SF Mono", "Menlo", "Monaco", monospace;--radius-sm: 8px;--radius-md: 12px;--radius-lg: 16px;--radius-xl: 20px;--radius-full: 980px;--ease-out: cubic-bezier(.25, .46, .45, .94);--transition-fast: .2s var(--ease-out);--transition-normal: .3s var(--ease-out)}[data-theme=dark]{--bg-primary: #000000;--bg-secondary: #1d1d1f;--bg-tertiary: #161617;--bg-card: #1d1d1f;--bg-hover: rgba(255, 255, 255, .08);--text-primary: #f5f5f7;--text-secondary: #a1a1a6;--text-tertiary: #6e6e73;--border-color: rgba(255, 255, 255, .08);--border-strong: rgba(255, 255, 255, .12);--shadow-sm: 0 2px 8px rgba(0, 0, 0, .3);--shadow-md: 0 4px 20px rgba(0, 0, 0, .4);--shadow-lg: 0 12px 40px rgba(0, 0, 0, .5);--shadow-card: 0 2px 12px rgba(0, 0, 0, .3)}*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}html{-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;text-rendering:optimizeLegibility}body{font-family:var(--font-sans);background:var(--bg-primary);color:var(--text-primary);line-height:1.5;font-size:17px;transition:background var(--transition-normal),color var(--transition-normal)}h1,h2,h3,h4,h5,h6{font-weight:600;letter-spacing:-.02em;color:var(--text-primary)}h1{font-size:48px;line-height:1.1;font-weight:700}h2{font-size:40px;line-height:1.1}h3{font-size:32px;line-height:1.15}h4{font-size:24px;line-height:1.2}h5{font-size:20px;line-height:1.25}h6{font-size:17px;line-height:1.3}p{color:var(--text-secondary);line-height:1.6}a{color:var(--accent);text-decoration:none;transition:color var(--transition-fast)}a:hover{color:var(--accent-hover)}.container{max-width:980px;margin:0 auto;padding:0 22px}.container-wide{max-width:1200px;margin:0 auto;padding:0 22px}.container-fluid{width:100%;padding:0 22px}.nav{position:fixed;top:0;left:0;right:0;z-index:1000;height:48px;background:rgba(251,251,253,.8);backdrop-filter:saturate(180%) blur(20px);-webkit-backdrop-filter:saturate(180%) blur(20px);border-bottom:1px solid var(--border-color);transition:background var(--transition-normal)}[data-theme=dark] .nav{background:rgba(22,22,23,.8)}.nav-inner{max-width:1024px;margin:0 auto;height:100%;display:flex;align-items:center;justify-content:space-between;padding:0 22px}.nav-logo{font-size:21px;font-weight:600;color:var(--text-primary);letter-spacing:-.02em}.nav-menu{display:flex;align-items:center;gap:32px}.nav-link{font-size:14px;color:var(--text-secondary);transition:color var(--transition-fast)}.nav-link:hover,.nav-link.active{color:var(--text-primary)}.nav-actions{display:flex;align-items:center;gap:16px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;font-family:var(--font-sans);font-size:17px;font-weight:400;padding:12px 24px;border-radius:var(--radius-full);border:none;cursor:pointer;transition:all var(--transition-fast);white-space:nowrap}.btn-primary{background:var(--accent);color:#fff}.btn-primary:hover{background:var(--accent-hover)}.btn-secondary{background:transparent;color:var(--accent)}.btn-secondary:hover{background:var(--bg-hover)}.btn-outline{background:transparent;color:var(--accent);border:1px solid var(--accent)}.btn-outline:hover{background:var(--accent);color:#fff}.btn-sm{font-size:14px;padding:8px 16px}.btn-lg{font-size:19px;padding:16px 32px}.card{background:var(--bg-card);border-radius:var(--radius-lg);border:1px solid var(--border-color);overflow:hidden;transition:transform var(--transition-fast),box-shadow var(--transition-fast)}.card:hover{transform:translateY(-2px);box-shadow:var(--shadow-card)}.card-body{padding:24px}.card-title{font-size:21px;font-weight:600;margin-bottom:8px;color:var(--text-primary)}.card-text{font-size:15px;color:var(--text-secondary);line-height:1.5}.form-group{margin-bottom:20px}.form-label{display:block;font-size:15px;font-weight:500;color:var(--text-primary);margin-bottom:8px}.form-input{width:100%;padding:14px 16px;font-family:var(--font-sans);font-size:17px;color:var(--text-primary);background:var(--bg-secondary);border:1px solid var(--border-color);border-radius:var(--radius-md);transition:border-color var(--transition-fast),box-shadow var(--transition-fast)}.form-input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px #0071e326}.form-input::-moz-placeholder{color:var(--text-tertiary)}.form-input::placeholder{color:var(--text-tertiary)}.hero{padding:120px 0 80px;text-align:center}.hero-title{font-size:56px;font-weight:700;letter-spacing:-.03em;margin-bottom:16px;background:linear-gradient(180deg,var(--text-primary) 0%,var(--text-secondary) 100%);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.hero-subtitle{font-size:24px;color:var(--text-secondary);max-width:600px;margin:0 auto 32px;line-height:1.4}.hero-actions{display:flex;justify-content:center;gap:16px;flex-wrap:wrap}.section{padding:80px 0}.section-alt{background:var(--bg-secondary)}.section-title{font-size:40px;font-weight:600;text-align:center;margin-bottom:16px}.section-subtitle{font-size:19px;color:var(--text-secondary);text-align:center;max-width:600px;margin:0 auto 48px}.grid{display:grid;gap:24px}.grid-2{grid-template-columns:repeat(2,1fr)}.grid-3{grid-template-columns:repeat(3,1fr)}.grid-4{grid-template-columns:repeat(4,1fr)}@media (max-width: 768px){.grid-2,.grid-3,.grid-4{grid-template-columns:1fr}}.course-card{background:var(--bg-card);border-radius:var(--radius-lg);overflow:hidden;border:1px solid var(--border-color);transition:transform var(--transition-fast),box-shadow var(--transition-fast)}.course-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-md)}.course-cover{aspect-ratio:16/9;background:linear-gradient(135deg,#667eea 0%,#764ba2 100%);display:flex;align-items:center;justify-content:center;font-size:48px}.course-cover img{width:100%;height:100%;-o-object-fit:cover;object-fit:cover}.course-content{padding:20px}.course-title{font-size:19px;font-weight:600;margin-bottom:8px;color:var(--text-primary);display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}.course-desc{font-size:15px;color:var(--text-secondary);margin-bottom:16px;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}.course-meta{display:flex;align-items:center;justify-content:space-between}.course-price{font-size:19px;font-weight:600;color:var(--accent)}.course-price.free{color:#34c759}.course-stats{display:flex;align-items:center;gap:12px;font-size:13px;color:var(--text-tertiary)}.badge{display:inline-flex;align-items:center;padding:4px 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var(--transition-fast);z-index:100}.dropdown.show{opacity:1;visibility:visible;transform:translateY(0)}.dropdown-item{display:flex;align-items:center;gap:12px;padding:12px 18px;font-size:16px;color:var(--text-secondary);cursor:pointer;transition:background var(--transition-fast)}.dropdown-item:hover{background:var(--bg-hover);color:var(--text-primary)}.dropdown-divider{height:1px;background:var(--border-color);margin:4px 0}.theme-toggle{width:32px;height:32px;border-radius:50%;border:none;background:var(--bg-hover);color:var(--text-secondary);cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all var(--transition-fast)}.theme-toggle:hover{background:var(--bg-secondary);color:var(--text-primary)}.footer{padding:48px 0;background:var(--bg-secondary);border-top:1px solid var(--border-color)}.footer-content{display:flex;justify-content:space-between;align-items:center}.footer-text{font-size:13px;color:var(--text-tertiary)}.footer-links{display:flex;gap:24px}.footer-link{font-size:13px;color:var(--text-tertiary)}.footer-link:hover{color:var(--text-secondary)}.stat{text-align:center;padding:24px}.stat-value{font-size:48px;font-weight:700;color:var(--text-primary);letter-spacing:-.02em}.stat-label{font-size:15px;color:var(--text-secondary);margin-top:4px}.loading{display:flex;align-items:center;justify-content:center;padding:48px}.spinner{width:24px;height:24px;border:2px solid var(--border-color);border-top-color:var(--accent);border-radius:50%;animation:spin .8s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}.toast{position:fixed;top:64px;right:22px;padding:14px 20px;background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-md);box-shadow:var(--shadow-lg);font-size:15px;color:var(--text-primary);transform:translate(120%);transition:transform var(--transition-normal);z-index:2000}.toast.show{transform:translate(0)}@media (max-width: 768px){body{font-size:15px}h1{font-size:32px}h2{font-size:28px}h3{font-size:24px}.hero{padding:80px 0 60px}.hero-title{font-size:36px}.hero-subtitle{font-size:19px}.section{padding:60px 0}.section-title{font-size:28px}.nav-menu{display:none}.stat-value{font-size:36px}}::-webkit-scrollbar{width:8px;height:8px}::-webkit-scrollbar-track{background:var(--bg-secondary)}::-webkit-scrollbar-thumb{background:var(--border-strong);border-radius:4px}::-webkit-scrollbar-thumb:hover{background:var(--text-tertiary)}::-moz-selection{background:rgba(0,113,227,.2)}::selection{background:rgba(0,113,227,.2)}