:root{--color-bg:#f8f9fa;--color-surface:#ffffff;--color-surface-alt:#f1f3f5;--color-text:#212529;--color-text-muted:#6c757d;--color-primary:#4361ee;--color-primary-hover:#3a56d4;--color-primary-light:#eef0ff;--color-success:#2ecc71;--color-success-light:#eafaf1;--color-warning:#f39c12;--color-warning-light:#fef9e7;--color-danger:#e74c3c;--color-danger-light:#fdedec;--color-info:#3498db;--color-info-light:#ebf5fb;--color-border:#dee2e6;--color-code-bg:#1e1e2e;--color-code-text:#cdd6f4;--color-tag:#89b4fa;--color-attr:#a6e3a1;--color-value:#f9e2af;--color-comment:#6c7086;--font-sans:'Segoe UI',system-ui,-apple-system,sans-serif;--font-mono:'Cascadia Code','Fira Code','JetBrains Mono','Consolas',monospace;--radius:8px;--radius-lg:12px;--shadow-sm:0 1px 3px rgba(0,0,0,0.08);--shadow-md:0 4px 12px rgba(0,0,0,0.1);--shadow-lg:0 8px 30px rgba(0,0,0,0.12);--transition:0.2s ease;--max-width:900px}[data-theme="light"]{--color-bg:#f8f9fa;--color-surface:#ffffff;--color-surface-alt:#f1f3f5;--color-text:#212529;--color-text-muted:#6c757d;--color-primary:#0284c7;--color-primary-hover:#0369a1;--color-primary-light:#eef0ff;--color-success:#16a34a;--color-success-light:#eafaf1;--color-warning:#d97706;--color-warning-light:#fef9e7;--color-danger:#dc2626;--color-danger-light:#fdedec;--color-info:#2563eb;--color-info-light:#ebf5fb;--color-border:#dee2e6}[data-theme="dark"]{--color-bg:#0a0e1a;--color-surface:#141b2d;--color-surface-alt:#1a233a;--color-text:#c8d6e5;--color-text-muted:#8395a7;--color-primary:#00d4ff;--color-primary-hover:#00b8e6;--color-primary-light:rgba(0,212,255,0.1);--color-success:#00ff88;--color-success-light:rgba(0,255,136,0.1);--color-warning:#ff9f43;--color-warning-light:rgba(255,159,67,0.1);--color-danger:#ff6b6b;--color-danger-light:rgba(255,107,107,0.1);--color-info:#54a0ff;--color-info-light:rgba(84,160,255,0.1);--color-border:rgba(0,212,255,0.15);--shadow-sm:0 1px 3px rgba(0,0,0,0.3);--shadow-md:0 4px 12px rgba(0,0,0,0.4);--shadow-lg:0 8px 30px rgba(0,0,0,0.5)}*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}html{scroll-behavior:smooth;font-size:16px}body{font-family:var(--font-sans);background:var(--color-bg);color:var(--color-text);line-height:1.7;min-height:100vh}.top-nav{background:var(--color-surface);border-bottom:1px solid var(--color-border);padding:0.75rem 1.5rem;position:sticky;top:0;z-index:100;box-shadow:var(--shadow-sm)}.top-nav-inner{max-width:1200px;margin:0 auto;display:flex;align-items:center;justify-content:space-between;gap:1rem}.top-nav .logo{font-size:1.25rem;font-weight:700;color:var(--color-primary);text-decoration:none;display:flex;align-items:center;gap:0.5rem}.top-nav .logo span{background:var(--color-primary);color:white;padding:2px 8px;border-radius:4px;font-size:0.75rem;font-weight:600}.breadcrumb{display:flex;align-items:center;gap:0.4rem;font-size:0.85rem;color:var(--color-text-muted);padding:1rem 0 0;max-width:var(--max-width);margin:0 auto;flex-wrap:wrap}.breadcrumb a{color:var(--color-primary);text-decoration:none}.breadcrumb a:hover{text-decoration:underline}.breadcrumb .separator{color:var(--color-text-muted);font-size:0.75rem}.lesson-container{max-width:var(--max-width);margin:0 auto;padding:1.5rem 1.5rem 4rem}.lesson-header{margin-bottom:2rem;padding-bottom:1.5rem;border-bottom:2px solid var(--color-border)}.lesson-header .chapter-label{display:inline-block;background:var(--color-primary-light);color:var(--color-primary);padding:4px 12px;border-radius:20px;font-size:0.8rem;font-weight:600;margin-bottom:0.75rem;text-transform:uppercase;letter-spacing:0.5px}.lesson-header h1{font-size:2rem;font-weight:800;line-height:1.2;margin-bottom:0.75rem}.lesson-header .subtitle{font-size:1.1rem;color:var(--color-text-muted);line-height:1.5}.learning-objectives{background:var(--color-info-light);border:1px solid var(--color-info);border-left:4px solid var(--color-info);border-radius:var(--radius);padding:1.25rem 1.5rem;margin-bottom:2rem}.learning-objectives h3{color:var(--color-info);font-size:0.95rem;font-weight:700;margin-bottom:0.75rem;display:flex;align-items:center;gap:0.5rem}.learning-objectives ul{list-style:none;padding:0}.learning-objectives li{padding:0.3rem 0;padding-left:1.5rem;position:relative;font-size:0.95rem}.learning-objectives li::before{content:'✓';position:absolute;left:0;color:var(--color-info);font-weight:700}.content-section{margin-bottom:2.5rem}.content-section h2{font-size:1.5rem;font-weight:700;margin-bottom:1rem;padding-bottom:0.5rem;border-bottom:1px solid var(--color-border)}.content-section h3{font-size:1.2rem;font-weight:600;margin:1.5rem 0 0.75rem}.content-section p{margin-bottom:1rem;font-size:1rem}.content-section ul,.content-section ol{margin:0.75rem 0 1rem 1.5rem}.content-section li{margin-bottom:0.4rem}.analogy-box{background:var(--color-warning-light);border:1px solid var(--color-warning);border-left:4px solid var(--color-warning);border-radius:var(--radius);padding:1.25rem 1.5rem;margin:1.5rem 0}.analogy-box h4{color:var(--color-warning);font-size:0.9rem;font-weight:700;margin-bottom:0.5rem;display:flex;align-items:center;gap:0.5rem}.pro-tip{background:var(--color-success-light);border:1px solid var(--color-success);border-left:4px solid var(--color-success);border-radius:var(--radius);padding:1.25rem 1.5rem;margin:1.5rem 0}.pro-tip h4{color:var(--color-success);font-size:0.9rem;font-weight:700;margin-bottom:0.5rem}.warning-box{background:var(--color-danger-light);border:1px solid var(--color-danger);border-left:4px solid var(--color-danger);border-radius:var(--radius);padding:1.25rem 1.5rem;margin:1.5rem 0}.warning-box h4{color:var(--color-danger);font-size:0.9rem;font-weight:700;margin-bottom:0.5rem}.info-box{background:var(--color-info-light);border:1px solid var(--color-info);border-left:4px solid var(--color-info);border-radius:var(--radius);padding:1.25rem 1.5rem;margin:1.5rem 0}.info-box h4{color:var(--color-info);font-size:0.9rem;font-weight:700;margin-bottom:0.5rem}.code-editor-wrapper{background:var(--color-code-bg);border-radius:var(--radius-lg);overflow:hidden;margin:1.5rem 0;box-shadow:var(--shadow-md)}.code-editor-header{display:flex;align-items:center;justify-content:space-between;padding:0.6rem 1rem;background:rgba(0,0,0,0.2);border-bottom:1px solid rgba(255,255,255,0.05)}.code-editor-header .dots{display:flex;gap:6px}.code-editor-header .dot{width:12px;height:12px;border-radius:50%}.code-editor-header .dot.red{background:#ff5f57}.code-editor-header .dot.yellow{background:#febc2e}.code-editor-header .dot.green{background:#28c840}.code-editor-header .file-label{color:var(--color-code-text);font-family:var(--font-mono);font-size:0.8rem;opacity:0.7}.code-editor-header .actions{display:flex;gap:0.5rem}.code-editor-header .btn-action{background:rgba(255,255,255,0.1);border:none;color:var(--color-code-text);padding:4px 12px;border-radius:4px;cursor:pointer;font-size:0.75rem;font-family:var(--font-sans);transition:var(--transition)}.code-editor-header .btn-action:hover{background:rgba(255,255,255,0.2)}.code-editor-header .btn-action.run-btn{background:var(--color-success);color:#fff}.code-editor-header .btn-action.run-btn:hover{background:#27ae60}.code-editor textarea{width:100%;min-height:200px;padding:1rem 1.25rem;background:transparent;color:var(--color-code-text);border:none;resize:vertical;font-family:var(--font-mono);font-size:0.9rem;line-height:1.6;tab-size:2;outline:none}.code-editor textarea::placeholder{color:var(--color-comment)}.preview-panel{border-top:1px solid rgba(255,255,255,0.1)}.preview-panel-header{display:flex;align-items:center;justify-content:space-between;padding:0.5rem 1rem;background:rgba(0,0,0,0.15);font-size:0.8rem;color:var(--color-code-text);opacity:0.7}.preview-frame{width:100%;min-height:150px;border:none;background:#fff}.code-block{background:var(--color-code-bg,#0d1117);border:1px solid rgba(0,212,255,0.25);border-radius:var(--radius,8px);padding:1.1rem 1.3rem;margin:1.2rem 0;overflow-x:auto;box-shadow:0 6px 25px rgba(0,0,0,0.5);font-family:'JetBrains Mono',var(--font-mono),monospace}.code-block pre,pre{margin:0;padding:0;background:transparent;border:none;overflow-x:auto}.code-block code,pre code{font-family:'JetBrains Mono',var(--font-mono),monospace;font-size:0.88rem;line-height:1.65;color:var(--color-code-text,#c9d1d9);white-space:pre !important;display:block;tab-size:2}.code-block .tag{color:var(--color-tag)}.code-block .attr{color:var(--color-attr)}.code-block .value{color:var(--color-value)}.code-block .comment{color:var(--color-comment);font-style:italic}code:not(.code-block code):not(pre code){background:var(--color-surface-alt,rgba(0,212,255,0.1));padding:2px 6px;border-radius:4px;font-family:'JetBrains Mono',var(--font-mono),monospace;font-size:0.88em;color:var(--color-primary,#00d4ff);border:1px solid rgba(0,212,255,0.2)}.exercise{background:var(--color-surface);border:2px solid var(--color-primary);border-radius:var(--radius-lg);padding:1.5rem;margin:2rem 0}.exercise h3{color:var(--color-primary);font-size:1.1rem;margin-bottom:0.75rem;display:flex;align-items:center;gap:0.5rem}.exercise .instructions{margin-bottom:1rem;font-size:0.95rem}.exercise .instructions ol{margin-left:1.25rem}.exercise .instructions li{margin-bottom:0.5rem}.quiz-section{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);padding:1.5rem;margin:2rem 0;box-shadow:var(--shadow-sm)}.quiz-section h3{font-size:1.1rem;margin-bottom:1rem;display:flex;align-items:center;gap:0.5rem}.quiz-question{margin-bottom:1.5rem;padding-bottom:1.5rem;border-bottom:1px solid var(--color-border)}.quiz-question:last-child{border-bottom:none;margin-bottom:0;padding-bottom:0}.quiz-question p{font-weight:600;margin-bottom:0.75rem}.quiz-question label{display:flex;align-items:flex-start;gap:0.5rem;padding:0.5rem 0.75rem;border-radius:var(--radius);cursor:pointer;transition:var(--transition);font-size:0.95rem}.quiz-question label:hover{background:var(--color-surface-alt)}.quiz-question input[type="radio"]{margin-top:4px;accent-color:var(--color-primary)}.quiz-feedback{margin-top:0.5rem;padding:0.75rem 1rem;border-radius:var(--radius);font-size:0.9rem;display:none}.quiz-feedback.correct{background:var(--color-success-light);color:var(--color-success);border:1px solid var(--color-success);display:block}.quiz-feedback.incorrect{background:var(--color-danger-light);color:var(--color-danger);border:1px solid var(--color-danger);display:block}.btn-check-answer{background:var(--color-primary);color:white;border:none;padding:0.5rem 1.25rem;border-radius:var(--radius);cursor:pointer;font-size:0.9rem;font-weight:600;margin-top:0.5rem;transition:var(--transition)}.btn-check-answer:hover{background:var(--color-primary-hover)}.key-takeaways{background:var(--color-primary-light);border:1px solid var(--color-primary);border-left:4px solid var(--color-primary);border-radius:var(--radius);padding:1.25rem 1.5rem;margin:2rem 0}.key-takeaways h3{color:var(--color-primary);font-size:0.95rem;font-weight:700;margin-bottom:0.75rem}.key-takeaways ul{list-style:none;padding:0}.key-takeaways li{padding:0.3rem 0 0.3rem 1.5rem;position:relative;font-size:0.95rem}.key-takeaways li::before{content:'📌';position:absolute;left:0}.lesson-nav{display:flex;justify-content:space-between;align-items:stretch;gap:1rem;margin-top:3rem;padding-top:2rem;border-top:2px solid var(--color-border)}.lesson-nav a{display:flex;flex-direction:column;padding:1rem 1.25rem;background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius);text-decoration:none;color:var(--color-text);transition:var(--transition);flex:1;max-width:48%;box-shadow:var(--shadow-sm)}.lesson-nav a:hover{border-color:var(--color-primary);box-shadow:var(--shadow-md);transform:translateY(-2px)}.lesson-nav a .nav-label{font-size:0.75rem;color:var(--color-text-muted);text-transform:uppercase;letter-spacing:0.5px;margin-bottom:0.25rem}.lesson-nav a .nav-title{font-weight:600;color:var(--color-primary);font-size:0.95rem}.lesson-nav a.next{text-align:right;margin-left:auto}.chapter-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:1.25rem;margin:1.5rem 0}.chapter-card{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);padding:1.5rem;text-decoration:none;color:var(--color-text);transition:var(--transition);box-shadow:var(--shadow-sm)}.chapter-card:hover{border-color:var(--color-primary);box-shadow:var(--shadow-md);transform:translateY(-3px)}.chapter-card .card-number{display:inline-flex;align-items:center;justify-content:center;width:36px;height:36px;background:var(--color-primary);color:white;border-radius:50%;font-weight:700;font-size:0.9rem;margin-bottom:0.75rem}.chapter-card h3{font-size:1.05rem;margin-bottom:0.5rem;font-weight:700}.chapter-card p{font-size:0.88rem;color:var(--color-text-muted);line-height:1.5}.lesson-list{list-style:none;padding:0;margin:1rem 0}.lesson-list li{border-bottom:1px solid var(--color-border)}.lesson-list li:last-child{border-bottom:none}.lesson-list a{display:flex;align-items:center;gap:1rem;padding:1rem 0.75rem;text-decoration:none;color:var(--color-text);transition:var(--transition);border-radius:var(--radius)}.lesson-list a:hover{background:var(--color-surface-alt);padding-left:1.25rem}.lesson-list .lesson-num{display:inline-flex;align-items:center;justify-content:center;width:32px;height:32px;background:var(--color-primary-light);color:var(--color-primary);border-radius:50%;font-weight:700;font-size:0.8rem;flex-shrink:0}.lesson-list .lesson-info h4{font-size:0.95rem;font-weight:600;margin-bottom:2px}.lesson-list .lesson-info p{font-size:0.82rem;color:var(--color-text-muted);margin:0}.progress-bar-wrapper{margin:1rem 0}.progress-bar-wrapper .label{font-size:0.8rem;color:var(--color-text-muted);margin-bottom:0.4rem}.progress-bar{width:100%;height:8px;background:var(--color-surface-alt);border-radius:4px;overflow:hidden}.progress-bar .fill{height:100%;background:var(--color-primary);border-radius:4px;transition:width 0.4s ease}.styled-table{width:100%;border-collapse:collapse;margin:1rem 0;font-size:0.9rem}.styled-table th,.styled-table td{padding:0.75rem 1rem;border:1px solid var(--color-border);text-align:left}.styled-table th{background:var(--color-surface-alt);font-weight:700;font-size:0.85rem;text-transform:uppercase;letter-spacing:0.3px}.styled-table tr:nth-child(even){background:var(--color-surface-alt)}.diagram{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius);padding:1.5rem;margin:1.5rem 0;text-align:center;overflow-x:auto}.diagram img{max-width:100%;height:auto}.diagram .ascii-art{font-family:var(--font-mono);font-size:0.8rem;white-space:pre;text-align:left;display:inline-block;line-height:1.4}.theme-toggle{background:var(--color-surface-alt);border:1px solid var(--color-border);width:40px;height:40px;border-radius:50%;cursor:pointer;display:flex;align-items:center;justify-content:center;font-size:1.1rem;transition:var(--transition)}.theme-toggle:hover{background:var(--color-primary-light);border-color:var(--color-primary)}.site-footer{max-width:var(--max-width);margin:0 auto;padding:2rem 1.5rem;text-align:center;color:var(--color-text-muted);font-size:0.85rem;border-top:1px solid var(--color-border)}@media (max-width:768px){.lesson-header h1{font-size:1.5rem}.lesson-nav{flex-direction:column}.lesson-nav a{max-width:100%}.chapter-grid{grid-template-columns:1fr}.code-editor-header .actions{flex-wrap:wrap}}@media (max-width:480px){.lesson-container{padding:1rem}.breadcrumb{padding:0.75rem 0 0;font-size:0.78rem}}.nav-links{display:flex;align-items:center;gap:1rem}.nav-links .nav-link{font-size:0.85rem;font-weight:600;color:var(--color-text-muted);text-decoration:none;transition:var(--transition)}.nav-links .nav-link:hover,.nav-links .nav-link--active{color:var(--color-primary)}.btn-solution-toggle{display:inline-flex;align-items:center;gap:0.4rem;border:none;font-size:0.85rem;font-weight:600;font-family:var(--font-sans);transition:var(--transition)}.btn-solution-toggle:hover{opacity:0.85;transform:translateY(-1px)}.solution-content pre,.solution-content code{white-space:pre-wrap;word-break:break-word}.lesson-body h3{font-size:1.15rem;font-weight:600;margin:1.5rem 0 0.75rem}.lesson-body h4{font-size:1rem;font-weight:600;margin:1.25rem 0 0.5rem}.lesson-body table{width:100%;border-collapse:collapse;margin:1rem 0;font-size:0.88rem;overflow-x:auto;display:block}.lesson-body th,.lesson-body td{padding:0.6rem 0.75rem;border:1px solid var(--color-border);text-align:left}.lesson-body th{background:var(--color-surface-alt);font-weight:700;font-size:0.82rem;text-transform:uppercase;letter-spacing:0.3px}.lesson-body tr:nth-child(even){background:var(--color-surface-alt)}.lesson-body blockquote{border-left:3px solid var(--color-primary);padding:0.5rem 1rem;margin:1rem 0;color:var(--color-text-muted);background:var(--color-surface-alt);border-radius:0 var(--radius) var(--radius) 0}.lesson-body pre{background:var(--color-code-bg);color:var(--color-code-text);padding:1rem 1.25rem;border-radius:var(--radius);overflow-x:auto;font-family:var(--font-mono);font-size:0.88rem;line-height:1.6;margin:1rem 0;box-shadow:var(--shadow-sm)}.lesson-body pre code{background:none;color:inherit;padding:0;font-size:inherit}.lesson-body img{max-width:100%;height:auto;border-radius:var(--radius)}.lesson-body details{background:var(--color-surface-alt);border:1px solid var(--color-border);border-radius:var(--radius);padding:0.75rem 1rem;margin:1rem 0}.lesson-body details summary{cursor:pointer;font-weight:600;color:var(--color-primary);font-size:0.9rem}.lesson-body details[open] summary{margin-bottom:0.75rem}