:root{--bg-dark: #090d16;--bg-card: rgba(17, 24, 39, .75);--bg-card-hover: rgba(30, 41, 59, .85);--bg-sidebar: #0d1322;--bg-navbar: rgba(13, 19, 34, .85);--bg-code: #050811;--border-color: rgba(255, 255, 255, .08);--border-glow: rgba(59, 130, 246, .3);--text-main: #f1f5f9;--text-muted: #94a3b8;--text-dim: #64748b;--accent-blue: #3b82f6;--accent-cyan: #06b6d4;--accent-purple: #8b5cf6;--accent-green: #10b981;--accent-amber: #f59e0b;--gradient-brand: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 50%, #06b6d4 100%);--gradient-card: linear-gradient(180deg, rgba(255, 255, 255, .04) 0%, rgba(255, 255, 255, .01) 100%);--font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;--font-mono: "Fira Code", monospace;--radius-sm: 8px;--radius-md: 12px;--radius-lg: 18px;--shadow-glow: 0 0 25px rgba(59, 130, 246, .15);--shadow-card: 0 10px 30px -10px rgba(0, 0, 0, .5)}*{box-sizing:border-box;margin:0;padding:0}body{background-color:var(--bg-dark);color:var(--text-main);font-family:var(--font-sans);line-height:1.6;overflow-x:hidden;-webkit-font-smoothing:antialiased}::-webkit-scrollbar{width:6px;height:6px}::-webkit-scrollbar-track{background:var(--bg-dark)}::-webkit-scrollbar-thumb{background:#1e293b;border-radius:4px}::-webkit-scrollbar-thumb:hover{background:var(--accent-blue)}.app-container{display:flex;flex-direction:column;min-height:100vh;background:radial-gradient(circle at 50% 0%,rgba(59,130,246,.08),transparent 40%),radial-gradient(circle at 100% 50%,rgba(139,92,246,.05),transparent 40%)}.main-layout{display:flex;flex:1;margin-top:64px}.navbar{position:fixed;top:0;left:0;right:0;height:64px;background:var(--bg-navbar);backdrop-filter:blur(16px);-webkit-backdrop-filter:blur(16px);border-bottom:1px solid var(--border-color);display:flex;align-items:center;justify-content:space-between;padding:0 24px;z-index:100}.navbar-brand{display:flex;align-items:center;gap:12px;font-weight:800;font-size:1.15rem;background:var(--gradient-brand);-webkit-background-clip:text;-webkit-text-fill-color:transparent;cursor:pointer}.navbar-search{display:flex;align-items:center;background:#ffffff0d;border:1px solid var(--border-color);border-radius:var(--radius-md);padding:6px 14px;width:320px;transition:all .2s ease}.navbar-search:focus-within{border-color:var(--accent-blue);box-shadow:0 0 12px #3b82f640;background:#ffffff14}.navbar-search input{background:transparent;border:none;outline:none;color:var(--text-main);font-family:inherit;font-size:.9rem;margin-left:8px;width:100%}.navbar-actions{display:flex;align-items:center;gap:16px}.sidebar{width:310px;background:var(--bg-sidebar);border-right:1px solid var(--border-color);display:flex;flex-direction:column;position:fixed;top:64px;bottom:0;overflow-y:auto;padding:20px 14px;transition:transform .3s ease;z-index:90}.sidebar-header{font-size:.75rem;font-weight:700;text-transform:uppercase;letter-spacing:.08em;color:var(--text-dim);margin-bottom:12px;padding-left:8px}.sidebar-item{display:flex;align-items:center;gap:12px;padding:10px 12px;border-radius:var(--radius-sm);color:var(--text-muted);cursor:pointer;transition:all .2s ease;margin-bottom:4px;border:1px solid transparent}.sidebar-item:hover{background:#ffffff0a;color:var(--text-main)}.sidebar-item.active{background:#3b82f61f;border-color:#3b82f64d;color:#60a5fa;font-weight:600;box-shadow:0 0 15px #3b82f61a}.sidebar-number{font-family:var(--font-mono);font-size:.8rem;font-weight:700;color:var(--accent-blue);background:#3b82f626;padding:2px 6px;border-radius:4px}.sidebar-status-badge{margin-left:auto;font-size:.68rem;padding:2px 6px;border-radius:10px;font-weight:600;text-transform:uppercase}.badge-available{background:#10b98126;color:#34d399}.badge-planned{background:#f59e0b1f;color:#fbbf24}.content-area{flex:1;margin-left:310px;padding:32px 40px 80px;max-width:1000px}.lesson-banner{background:var(--bg-card);background-image:var(--gradient-card);-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);border:1px solid var(--border-color);border-radius:var(--radius-lg);padding:32px;margin-bottom:36px;box-shadow:var(--shadow-card);position:relative;overflow:hidden}.lesson-banner:before{content:"";position:absolute;top:0;left:0;width:4px;height:100%;background:var(--gradient-brand)}.lesson-category{display:inline-flex;align-items:center;gap:6px;font-size:.8rem;font-weight:700;color:var(--accent-cyan);text-transform:uppercase;letter-spacing:.05em;margin-bottom:8px}.lesson-title{font-size:2.2rem;font-weight:800;margin-bottom:12px;letter-spacing:-.02em}.lesson-meta-bar{display:flex;align-items:center;gap:16px;margin-top:16px;font-size:.85rem;color:var(--text-muted)}.meta-chip{display:flex;align-items:center;gap:6px;background:#ffffff0d;padding:4px 10px;border-radius:20px;border:1px solid var(--border-color)}.section-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-md);padding:28px;margin-bottom:28px;transition:border-color .2s ease}.section-card:hover{border-color:#ffffff26}.section-title{font-size:1.4rem;font-weight:700;margin-bottom:16px;color:#f8fafc}.section-body{color:#cbd5e1;font-size:1rem;line-height:1.7;margin-bottom:20px}.section-body h2,.section-body h3,.section-body h4{color:#38bdf8;margin:20px 0 10px;font-weight:700}.section-body h3{font-size:1.15rem}.section-body p{margin-bottom:12px;line-height:1.7}.section-body strong{color:#f8fafc;font-weight:700}.section-body ul,.section-body ol{margin:10px 0 16px 24px;color:#cbd5e1}.section-body li{margin-bottom:6px;line-height:1.6}.section-body code{background:#3b82f626;color:#93c5fd;font-family:var(--font-mono);font-size:.88rem;padding:2px 6px;border-radius:4px}.section-body table{width:100%;border-collapse:collapse;margin:18px 0}.section-body th,.section-body td{border:1px solid var(--border-color);padding:10px 14px;text-align:left}.section-body th{background:#ffffff0d;color:#38bdf8;font-weight:700}.code-box{background:var(--bg-code);border:1px solid var(--border-color);border-radius:var(--radius-sm);margin-top:16px;overflow:hidden}.code-box-header{display:flex;align-items:center;justify-content:space-between;background:#ffffff08;padding:8px 16px;border-bottom:1px solid var(--border-color);font-size:.8rem;font-weight:600;color:var(--text-muted)}.code-box-actions{display:flex;align-items:center;gap:8px}.btn-icon{display:flex;align-items:center;gap:6px;background:#ffffff0d;border:1px solid var(--border-color);color:var(--text-muted);padding:4px 10px;border-radius:6px;font-size:.75rem;cursor:pointer;transition:all .2s ease}.btn-icon:hover{background:#3b82f633;color:#fff;border-color:var(--accent-blue)}.btn-primary{background:var(--gradient-brand);color:#fff;font-weight:600;padding:8px 18px;border-radius:var(--radius-sm);border:none;cursor:pointer;display:flex;align-items:center;gap:8px;transition:transform .2s ease,box-shadow .2s ease}.btn-primary:hover{transform:translateY(-1px);box-shadow:0 4px 20px #3b82f659}.code-content{font-family:var(--font-mono);font-size:.9rem;color:#e2e8f0;padding:16px;overflow-x:auto;white-space:pre;line-height:1.5}.quiz-container{margin-top:40px}.quiz-card{background:var(--bg-card);border:1px solid var(--border-color);border-radius:var(--radius-md);padding:24px;margin-bottom:20px}.quiz-question{font-size:1.1rem;font-weight:600;margin-bottom:16px}.quiz-options{display:flex;flex-direction:column;gap:10px}.quiz-option-btn{background:#ffffff08;border:1px solid var(--border-color);border-radius:var(--radius-sm);padding:12px 16px;color:var(--text-main);text-align:left;font-size:.95rem;cursor:pointer;transition:all .2s ease;display:flex;align-items:center;justify-content:space-between}.quiz-option-btn:hover{background:#3b82f61a;border-color:#3b82f64d}.quiz-option-btn.correct{background:#10b9812e;border-color:#10b981;color:#6ee7b7}.quiz-option-btn.wrong{background:#ef44442e;border-color:#ef4444;color:#fca5a5}.quiz-explanation{margin-top:14px;padding:12px 16px;background:#3b82f61a;border-left:3px solid var(--accent-blue);border-radius:4px;font-size:.88rem;color:#bfdbfe}.playground-drawer{position:fixed;bottom:0;right:24px;width:500px;height:480px;background:var(--bg-sidebar);border:1px solid var(--border-color);border-radius:var(--radius-lg) var(--radius-lg) 0 0;box-shadow:0 -10px 40px #000000b3;display:flex;flex-direction:column;z-index:120;transition:transform .3s ease}.playground-header{display:flex;align-items:center;justify-content:space-between;padding:12px 18px;background:#ffffff0a;border-bottom:1px solid var(--border-color);font-weight:700;font-size:.9rem}.playground-body{flex:1;display:flex;flex-direction:column;padding:14px;gap:12px}.playground-editor{flex:1;background:var(--bg-code);border:1px solid var(--border-color);border-radius:var(--radius-sm);padding:12px;color:#e2e8f0;font-family:var(--font-mono);font-size:.88rem;resize:none;outline:none}.playground-output{height:130px;background:#02040a;border:1px solid var(--border-color);border-radius:var(--radius-sm);padding:10px;font-family:var(--font-mono);font-size:.82rem;color:#38bdf8;overflow-y:auto;white-space:pre-wrap}.progress-bar-bg{width:120px;height:8px;background:#ffffff1a;border-radius:4px;overflow:hidden}.progress-bar-fill{height:100%;background:var(--gradient-brand);transition:width .3s ease}