:root{--primary-color: #4f46e5;--primary-dark: #4338ca;--secondary-color: #ec4899;--bg-color: #ffffff;--bg-secondary: #f9fafb;--text-color: #1f2937;--text-secondary: #4b5563;--border-color: #e5e7eb;--card-shadow: 0 1px 3px 0 rgba(0, 0, 0, .1), 0 1px 2px 0 rgba(0, 0, 0, .06);--card-shadow-hover: 0 10px 15px -3px rgba(0, 0, 0, .1), 0 4px 6px -2px rgba(0, 0, 0, .05);--transition: all .3s ease}[data-theme=dark]{--bg-color: #0f172a;--bg-secondary: #1e293b;--text-color: #f1f5f9;--text-secondary: #94a3b8;--border-color: #334155;--card-shadow: 0 4px 6px -1px rgba(0, 0, 0, .3);--card-shadow-hover: 0 10px 15px -3px rgba(0, 0, 0, .4)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,sans-serif;background-color:var(--bg-color);color:var(--text-color);line-height:1.6;transition:var(--transition)}.container{max-width:1200px;margin:0 auto;padding:0 20px}.navbar{background-color:var(--bg-color);border-bottom:1px solid var(--border-color);position:sticky;top:0;z-index:1000;box-shadow:0 2px 4px #0000000d}.navbar .container{display:flex;justify-content:space-between;align-items:center;padding:1rem 20px}.nav-brand{display:flex;align-items:center;gap:.5rem;font-size:1.25rem;font-weight:700;color:var(--primary-color)}.nav-brand a{text-decoration:none;color:inherit}.logo{font-size:1.5rem}.nav-menu{display:flex;list-style:none;gap:2rem;align-items:center}.nav-menu a{text-decoration:none;color:var(--text-color);font-weight:500;transition:var(--transition)}.nav-menu a:hover{color:var(--primary-color)}.nav-actions{display:flex;align-items:center;gap:.75rem}.lang-toggle{background:var(--bg-secondary);border:1px solid var(--border-color);padding:.4rem .875rem;border-radius:20px;cursor:pointer;transition:var(--transition);display:flex;align-items:center;gap:.375rem;font-size:.875rem;font-weight:500;color:var(--text-color)}.lang-toggle:hover{background:var(--border-color);color:var(--primary-color)}.lang-icon{font-size:1rem}.lang-text{font-size:.8125rem}.theme-toggle{background:var(--bg-secondary);border:1px solid var(--border-color);padding:.5rem 1rem;border-radius:20px;cursor:pointer;transition:var(--transition)}.theme-toggle:hover{background:var(--border-color)}.moon-icon,[data-theme=dark] .sun-icon{display:none}[data-theme=dark] .moon-icon{display:inline}.tutorial-nav{background:var(--bg-secondary);padding:1rem 0;border-bottom:1px solid var(--border-color)}.tutorial-nav .container{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:1rem}.progress-indicator{display:flex;align-items:center;gap:1rem}.progress-bar{width:200px;height:8px;background:var(--bg-color);border-radius:4px;overflow:hidden}.progress-fill{height:100%;background:linear-gradient(90deg,var(--primary-color),var(--secondary-color));transition:width .3s ease}.nav-buttons{display:flex;gap:1rem}.lesson-layout{display:flex;max-width:1400px;margin:0 auto;gap:2rem;padding:2rem 20px}.lesson-sidebar{width:280px;flex-shrink:0;position:sticky;top:2rem;height:fit-content;max-height:calc(100vh - 4rem);overflow-y:auto;background:var(--bg-secondary);border-radius:12px;padding:1.5rem;box-shadow:var(--card-shadow)}.sidebar-header{margin-bottom:1.5rem;padding-bottom:1rem;border-bottom:2px solid var(--border-color)}.sidebar-header h3{font-size:1.1rem;margin:0;color:var(--text-color)}.sidebar-nav{display:flex;flex-direction:column;gap:1.5rem}.sidebar-section{display:flex;flex-direction:column;gap:.5rem}.sidebar-section-title{font-size:.85rem;font-weight:700;text-transform:uppercase;letter-spacing:.05em;color:var(--text-secondary);margin-bottom:.25rem}.sidebar-link{display:flex;align-items:center;gap:.75rem;padding:.625rem .875rem;border-radius:8px;text-decoration:none;color:var(--text-secondary);transition:var(--transition);font-size:.9rem}.sidebar-link:hover{background:var(--bg-color);color:var(--primary-color);transform:translate(4px)}.sidebar-link.active{background:var(--primary-color);color:#fff;font-weight:600}.sidebar-number{display:flex;align-items:center;justify-content:center;width:24px;height:24px;min-width:24px;border-radius:6px;background:var(--bg-color);font-size:.75rem;font-weight:700;color:var(--text-secondary);transition:var(--transition)}.sidebar-link:hover .sidebar-number{background:var(--primary-color);color:#fff}.sidebar-link.active .sidebar-number{background:#ffffff40;color:#fff}.sidebar-text{flex:1}.lesson-container{flex:1;max-width:900px}.lesson-header{margin-bottom:3rem}.lesson-title{font-size:2.5rem;font-weight:800;margin-bottom:1rem;color:var(--text-color);line-height:1.2}.lesson-meta{display:flex;gap:1rem;color:var(--text-secondary);font-size:.875rem;flex-wrap:wrap}.lesson-content{line-height:1.8;font-size:1.0625rem}.lesson-content h2{font-size:1.875rem;margin-top:3rem;margin-bottom:1.5rem;color:var(--primary-color);font-weight:700}.lesson-content h3{font-size:1.5rem;margin-top:2rem;margin-bottom:1rem;color:var(--text-color);font-weight:600}.lesson-content p{margin-bottom:1.25rem}.lesson-content ul,.lesson-content ol{margin-bottom:1.25rem;padding-left:2rem}.lesson-content li{margin-bottom:.5rem}.practice-section{margin:3rem 0;border:2px solid var(--border-color);border-radius:12px;overflow:hidden;background:var(--bg-color)}.practice-header{background:linear-gradient(135deg,var(--primary-color),var(--primary-dark));color:#fff;padding:1.5rem;cursor:pointer;display:flex;justify-content:space-between;align-items:center;-webkit-user-select:none;user-select:none;transition:var(--transition)}.practice-header:hover{background:linear-gradient(135deg,var(--primary-dark),var(--primary-color))}.practice-title{font-size:1.25rem;font-weight:600;display:flex;align-items:center;gap:.5rem}.practice-toggle{font-size:1.5rem;transition:transform .3s ease}.practice-toggle.expanded{transform:rotate(180deg)}.practice-content{display:none}.practice-content.expanded{display:block;animation:slideDown .3s ease}@keyframes slideDown{0%{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.practice-grid{display:grid;grid-template-columns:1fr 1fr;gap:0;border-top:1px solid var(--border-color)}.practice-editor{padding:1.5rem;border-right:1px solid var(--border-color)}.practice-editor-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:1rem}.practice-editor-title{font-weight:600;color:var(--primary-color)}.editor-toolbar{display:flex;gap:.25rem;flex-wrap:wrap}.editor-btn{padding:.375rem .75rem;background:var(--bg-secondary);border:1px solid var(--border-color);border-radius:4px;cursor:pointer;font-size:.8125rem;transition:var(--transition)}.editor-btn:hover{background:var(--primary-color);color:#fff;border-color:var(--primary-color)}.practice-editor textarea{width:100%;min-height:600px;height:100%;padding:1rem;border:none;background:var(--bg-color);color:var(--text-color);font-family:Monaco,Menlo,Ubuntu Mono,monospace;font-size:.9375rem;line-height:1.6;resize:none;outline:none}#markdown-editor:focus{outline:none;border-color:var(--primary-color);box-shadow:0 0 0 3px #6366f11a}.practice-preview{padding:1.5rem;background:var(--bg-secondary);overflow-y:auto;min-height:800px;max-height:800px}.practice-preview-title{font-weight:600;color:var(--primary-color);margin-bottom:1rem}#preview-content{line-height:1.7}#preview-content h1,#preview-content h2,#preview-content h3,#preview-content h4,#preview-content h5,#preview-content h6{margin-top:1.5rem;margin-bottom:.75rem;font-weight:600;line-height:1.3}#preview-content h1{font-size:2rem;border-bottom:2px solid var(--border-color);padding-bottom:.5rem}#preview-content h2{font-size:1.5rem;border-bottom:1px solid var(--border-color);padding-bottom:.5rem}#preview-content p{margin-bottom:1rem}#preview-content ul,#preview-content ol{margin-bottom:1rem;padding-left:2rem}#preview-content blockquote{border-left:4px solid var(--primary-color);padding-left:1rem;margin:1rem 0;color:var(--text-secondary);font-style:italic}#preview-content code{background:var(--bg-color);padding:.2rem .4rem;border-radius:4px;font-family:Monaco,Menlo,Ubuntu Mono,monospace;font-size:.9em}#preview-content pre{background:var(--bg-color);padding:1rem;border-radius:8px;overflow-x:auto;margin-bottom:1rem;border:1px solid var(--border-color)}#preview-content pre code{background:none;padding:0;border:none}#preview-content table{width:100%;border-collapse:collapse;margin-bottom:1rem}#preview-content th,#preview-content td{border:1px solid var(--border-color);padding:.75rem;text-align:left}#preview-content th{background:var(--bg-color);font-weight:600}#preview-content img{max-width:100%;height:auto;border-radius:8px;margin:1rem 0}#preview-content a{color:var(--primary-color);text-decoration:none}#preview-content a:hover{text-decoration:underline}.tips-box{background:linear-gradient(135deg,#6366f11a,#ec48991a);border:1px solid var(--primary-color);padding:1.5rem;border-radius:8px;margin:2rem 0}.tips-box strong{color:var(--primary-color);display:block;margin-bottom:.5rem}.warning-box{background:#ef44441a;border:1px solid #ef4444;padding:1.5rem;border-radius:8px;margin:2rem 0}.warning-box strong{color:#ef4444;display:block;margin-bottom:.5rem}.info-box{background:#3b82f61a;border:1px solid #3b82f6;padding:1.5rem;border-radius:8px;margin:2rem 0}.info-box strong{color:#3b82f6;display:block;margin-bottom:.5rem}.markdown-example{background:var(--bg-secondary);border:1px solid var(--border-color);border-radius:8px;padding:0;margin:1.5rem 0;overflow:hidden}.example-header{background:var(--bg-color);padding:.75rem 1rem;border-bottom:1px solid var(--border-color);font-size:.875rem;color:var(--text-secondary);font-weight:500}.markdown-example pre{margin:0;padding:1.5rem;border:none;background:transparent}.markdown-example code{font-family:Monaco,Menlo,Ubuntu Mono,monospace;font-size:.9375rem;line-height:1.6;background:none;padding:0}.practice-box{background:var(--bg-secondary);border-left:4px solid var(--secondary-color);padding:1.5rem;border-radius:8px;margin:2rem 0}.practice-box h3{color:var(--secondary-color);margin-bottom:1rem}.btn{padding:.875rem 2rem;border-radius:8px;text-decoration:none;font-weight:600;transition:var(--transition);border:2px solid transparent;cursor:pointer;display:inline-block}.btn-primary{background-color:var(--primary-color);color:#fff}.btn-primary:hover{background-color:var(--primary-dark);transform:translateY(-2px);box-shadow:0 10px 20px #6366f14d}.btn-secondary{background-color:transparent;color:var(--primary-color);border-color:var(--primary-color)}.btn-secondary:hover{background-color:var(--primary-color);color:#fff;transform:translateY(-2px)}.lesson-navigation{display:flex;justify-content:space-between;gap:1rem;margin-top:4rem;padding-top:2rem;border-top:2px solid var(--border-color)}.lesson-navigation .btn{flex:1;text-align:center}.complete-lesson-section{text-align:center;margin-top:3rem;padding:2rem;background:var(--bg-secondary);border-radius:12px}.complete-lesson-section h3{font-size:1.5rem;margin-bottom:1rem;color:var(--text-color)}#complete-lesson{font-size:1.1rem;padding:1rem 3rem;position:relative;overflow:hidden;transition:all .3s ease}#complete-lesson:before{content:"";position:absolute;top:50%;left:50%;width:0;height:0;border-radius:50%;background:#ffffff4d;transform:translate(-50%,-50%);transition:width .6s,height .6s}#complete-lesson:active:before{width:300px;height:300px}#complete-lesson.completed{background:linear-gradient(135deg,#10b981,#059669)!important;cursor:default;opacity:.8}#complete-lesson.completed:hover{transform:none!important;box-shadow:none!important}#complete-lesson.completed:after{content:" ✓";margin-left:.5rem}.hero{padding:5rem 0;text-align:center;background:linear-gradient(135deg,var(--bg-secondary) 0%,var(--bg-color) 100%)}.hero-title{font-size:3.5rem;font-weight:800;margin-bottom:1rem;line-height:1.2}.gradient-text{background:linear-gradient(135deg,var(--primary-color),var(--secondary-color));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.hero-subtitle{font-size:1.25rem;color:var(--text-secondary);margin-bottom:3rem}.hero-stats{display:flex;justify-content:center;gap:3rem;margin-bottom:3rem}.stat{text-align:center}.stat-number{font-size:2.5rem;font-weight:800;color:var(--primary-color)}.stat-label{color:var(--text-secondary);font-size:.875rem;margin-top:.5rem}.hero-cta{display:flex;gap:1rem;justify-content:center;flex-wrap:wrap}.features{padding:5rem 0;background-color:var(--bg-secondary)}.section-title{text-align:center;font-size:2.5rem;font-weight:700;margin-bottom:3rem}.features-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:2rem}.feature-card{background-color:var(--bg-color);padding:2rem;border-radius:12px;box-shadow:var(--card-shadow);transition:var(--transition)}.feature-card:hover{transform:translateY(-5px);box-shadow:var(--card-shadow-hover)}.feature-icon{font-size:3rem;margin-bottom:1rem}.feature-card h3{font-size:1.5rem;margin-bottom:.5rem;color:var(--text-color)}.feature-card p{color:var(--text-secondary);line-height:1.7}.footer{background-color:var(--bg-secondary);border-top:1px solid var(--border-color);padding:2rem 0;text-align:center;color:var(--text-secondary)}.footer p{margin-bottom:.5rem}@media (max-width: 768px){.hero-title{font-size:2.5rem}.hero-subtitle{font-size:1rem}.hero-stats{flex-direction:column;gap:2rem}.nav-menu{gap:1rem;font-size:.875rem}.features-grid,.practice-grid{grid-template-columns:1fr}.practice-editor{border-right:none;border-bottom:1px solid var(--border-color)}.lesson-navigation{flex-direction:column}.nav-buttons{flex-direction:column;width:100%}.nav-buttons .btn{width:100%}.lesson-title{font-size:2rem}.lesson-layout{flex-direction:column;padding:1rem}.lesson-sidebar{width:100%;position:static;max-height:none;order:-1;margin-bottom:1rem}.lesson-container{padding:1rem}.chapter-card{flex-direction:column;text-align:center}.chapter-number{min-width:auto}.chapter-meta{justify-content:center}.sidebar-nav{display:none}.sidebar-nav.mobile-expanded{display:flex}}.chapter-card{display:flex;align-items:center;gap:1.5rem;padding:1.5rem;background-color:var(--bg-secondary);border-radius:12px;text-decoration:none;color:var(--text-color);transition:var(--transition);border:2px solid transparent;margin-bottom:1rem}.chapter-card:hover{border-color:var(--primary-color);transform:translate(5px);box-shadow:var(--card-shadow)}.chapter-number{font-size:2rem;font-weight:800;color:var(--primary-color);opacity:.5;min-width:80px}.chapter-info{flex:1}.chapter-info h3{font-size:1.25rem;margin-bottom:.5rem;color:var(--text-color)}.chapter-info p{color:var(--text-secondary);margin-bottom:.5rem}.chapter-meta{display:flex;gap:1rem;font-size:.875rem;color:var(--text-secondary)}.chapter-status{font-size:1.5rem;color:var(--primary-color);opacity:0;transition:var(--transition)}.chapter-card:hover .chapter-status{opacity:1}.curriculum{padding:3rem 0}.curriculum-tabs{display:flex;justify-content:center;gap:1rem;margin-bottom:3rem;flex-wrap:wrap}.tab-btn{padding:.875rem 2rem;border:2px solid var(--border-color);background-color:var(--bg-color);color:var(--text-color);border-radius:8px;cursor:pointer;font-weight:600;transition:var(--transition)}.tab-btn:hover{border-color:var(--primary-color);color:var(--primary-color)}.tab-btn.active{background-color:var(--primary-color);color:#fff;border-color:var(--primary-color)}.tab-content{display:none}.tab-content.active{display:block;animation:fadeIn .3s ease}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}.chapter-list{display:flex;flex-direction:column;gap:1rem}