body { background-color: #0f172a; color: #e2e8f0; font-family: 'Inter', sans-serif; margin: 0; overflow-x: hidden; }
        
        .navbar {
            position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
            background: rgba(30, 41, 59, 0.8); backdrop-filter: blur(12px);
            padding: 15px 40px; display: flex; justify-content: space-between; 
            align-items: center; border-bottom: 1px solid rgba(51, 65, 85, 0.5); height: 70px;
        }
        .navbar h1 { margin: 0; font-size: 22px; color: #e2e8f0; display: flex; align-items: center; gap: 10px; font-weight: 700; }
        .navbar h1 i { color: #3b82f6; }
        
        .doc-wrapper {
            display: grid;
            grid-template-columns: 260px 1fr;
            max-width: 1200px;
            margin: 100px auto 60px;
            gap: 60px;
            padding: 0 30px;
        }

        .doc-sidebar {
            position: sticky;
            top: 110px;
            height: calc(100vh - 140px);
            overflow-y: auto;
            padding-right: 10px;
        }
        .doc-sidebar::-webkit-scrollbar { width: 4px; }
        .doc-sidebar::-webkit-scrollbar-thumb { background: #334155; border-radius: 4px; }

        .sidebar-nav { list-style: none; padding: 0; margin: 0; }
        .sidebar-nav li { margin-bottom: 4px; }
        .sidebar-nav a {
            display: flex; align-items: center; gap: 10px;
            padding: 10px 15px; color: #94a3b8; text-decoration: none;
            border-radius: 8px; transition: all 0.2s; font-size: 14px; font-weight: 500;
        }
        .sidebar-nav a:hover { background: #334155; color: #f1f5f9; }
        .sidebar-nav a.active { background: rgba(59, 130, 246, 0.1); color: #3b82f6; font-weight: 600; }
        .sidebar-nav .nav-header {
            font-size: 11px; text-transform: uppercase; letter-spacing: 0.08em;
            color: #64748b; margin: 25px 0 10px 15px; font-weight: 800;
        }

        .doc-content { min-width: 0; }

        .hero-header {
            margin-bottom: 50px;
            padding-bottom: 30px;
            border-bottom: 1px solid #334155;
        }
        .hero-title {
            font-size: 42px; font-weight: 800; letter-spacing: -0.02em; margin: 0 0 15px 0;
            background: linear-gradient(135deg, #f8fafc 0%, #94a3b8 100%);
            -webkit-background-clip: text; -webkit-text-fill-color: transparent;
        }
        .hero-subtitle { font-size: 18px; color: #94a3b8; line-height: 1.6; max-width: 800px; }

        .lang-switch { display: flex; justify-content: flex-end; margin-bottom: 20px; gap: 8px; }
        .lang-btn {
            background: #1e293b; border: 1px solid #334155; color: #94a3b8; padding: 6px 12px;
            border-radius: 6px; cursor: pointer; font-weight: 600; font-size: 13px; transition: all 0.2s;
        }
        .lang-btn:hover { border-color: #3b82f6; color: #e2e8f0; }
        .lang-btn.active { background: #3b82f6; color: white; border-color: #3b82f6; }

        .doc-section { margin-bottom: 60px; scroll-margin-top: 100px; }
        .doc-section h2 { 
            font-size: 28px; color: #f1f5f9; margin-bottom: 25px; font-weight: 700; 
            display: flex; align-items: center; gap: 12px;
        }
        .doc-section h3 { font-size: 20px; color: #e2e8f0; margin: 35px 0 15px; font-weight: 600; display: flex; align-items: center; gap: 10px; }
        .doc-section h3 i { color: #3b82f6; opacity: 0.8; }
        
        .doc-text { color: #cbd5e1; line-height: 1.75; margin-bottom: 20px; font-size: 16px; }
        
        /* Image styling */
        .doc-img {
            max-width: 100%;
            height: auto;
            border-radius: 8px;
            border: 1px solid #334155;
            margin: 20px 0;
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
        }

        .feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 20px; margin: 25px 0; }
        .feature-card {
            background: #1e293b; border: 1px solid #334155; border-radius: 12px; padding: 25px;
            transition: transform 0.2s, border-color 0.2s;
        }
        .feature-card:hover { transform: translateY(-2px); border-color: #3b82f6; }
        .feature-icon { 
            font-size: 24px; color: #3b82f6; margin-bottom: 15px; 
            background: rgba(59, 130, 246, 0.1); width: 48px; height: 48px; 
            display: flex; align-items: center; justify-content: center; border-radius: 10px;
        }
        .feature-title { font-weight: 700; color: #f1f5f9; margin-bottom: 8px; font-size: 18px; }
        .feature-desc { font-size: 14px; color: #94a3b8; line-height: 1.6; }

        .link-block {
            display: flex;
            align-items: center;
            gap: 20px;
            background: linear-gradient(135deg, rgba(59, 130, 246, 0.1), rgba(30, 41, 59, 0.5));
            border: 1px solid rgba(59, 130, 246, 0.3);
            padding: 20px 25px;
            border-radius: 12px;
            text-decoration: none;
            transition: all 0.3s ease;
            margin-top: 30px;
        }
        .link-block:hover {
            transform: translateY(-2px);
            border-color: #3b82f6;
            background: linear-gradient(135deg, rgba(59, 130, 246, 0.15), rgba(30, 41, 59, 0.6));
            box-shadow: 0 10px 30px rgba(0,0,0,0.2);
        }
        .link-icon {
            font-size: 28px;
            color: #3b82f6;
            background: rgba(59, 130, 246, 0.1);
            width: 54px;
            height: 54px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            flex-shrink: 0;
        }
        .link-content h4 { margin: 0 0 5px 0; color: #f1f5f9; font-size: 18px; font-weight: 700; display: flex; align-items: center; gap: 8px; }
        .link-content p { margin: 0; color: #94a3b8; font-size: 14px; line-height: 1.4; }
        .link-arrow { margin-left: auto; color: #3b82f6; font-size: 20px; transition: transform 0.2s; }
        .link-block:hover .link-arrow { transform: translateX(5px); }

        .table-explain { display: grid; grid-template-columns: 1fr; gap: 15px; margin: 20px 0; }
        .table-row-explain {
            display: grid; grid-template-columns: 120px 1fr; align-items: center;
            background: #172033; padding: 15px; border-radius: 8px; border: 1px solid #2a374a;
        }
        .col-name { font-weight: 700; color: #f1f5f9; font-size: 15px; }
        .col-desc { color: #94a3b8; font-size: 14px; line-height: 1.4; }

        .formula-box {
            background: #020617; border: 1px solid #1e293b; padding: 20px; margin: 20px 0;
            border-radius: 8px; font-family: 'Courier New', monospace; color: #e2e8f0; font-size: 14px;
            position: relative; overflow: hidden;
        }
        .formula-box::before {
            content: ''; position: absolute; top: 0; left: 0; bottom: 0; width: 4px; background: #8b5cf6;
        }

        .tag { display: inline-block; padding: 4px 10px; border-radius: 6px; font-size: 12px; font-weight: 600; margin-right: 6px; }
        .tag.green { background: rgba(16, 185, 129, 0.15); color: #34d399; }
        .tag.red { background: rgba(239, 68, 68, 0.15); color: #f87171; }
        .tag.blue { background: rgba(59, 130, 246, 0.15); color: #60a5fa; }

        .back-link {
            background: #334155; color: #e2e8f0; padding: 8px 16px; border-radius: 8px;
            text-decoration: none; font-weight: 500; display: flex; align-items: center; gap: 8px; transition: background 0.2s; font-size: 14px;
        }
        .back-link:hover { background: #475569; }

        .step-list {
            margin: 20px 0; padding-left: 20px; color: #cbd5e1;
        }
        .step-list li { margin-bottom: 10px; line-height: 1.6; }

        [data-lang="ru"] { display: none; }

        @media (max-width: 900px) {
            .doc-wrapper { grid-template-columns: 1fr; margin-top: 80px; }
            .doc-sidebar { display: none; }
            .hero-title { font-size: 32px; }
            .table-row-explain { grid-template-columns: 1fr; gap: 5px; }
            .link-block { flex-direction: column; text-align: center; gap: 15px; }
            .link-arrow { display: none; }
        }