:root {
            --bg-dark: #0a0a0f;
            --bg-card: #12121a;
            --bg-code: #1a1a2e;
            --neon-cyan: #00f5ff;
            --neon-magenta: #ff00ff;
            --neon-purple: #b366ff;
            --text-primary: #ffffff;
            --text-secondary: #a0a0b0;
            --border-color: #2a2a3a;
            --success-green: #4ec9b0;
            --warning-yellow: #dcdcaa;
        }

        * { margin: 0; padding: 0; box-sizing: border-box; }

        body {
            font-family: 'Space Grotesk', sans-serif;
            background: var(--bg-dark);
            color: var(--text-primary);
            line-height: 1.7;
            min-height: 100vh;
        }

        body::before {
            content: '';
            position: fixed;
            top: 0; left: 0; width: 100%; height: 100%;
            background:
                linear-gradient(90deg, rgba(0,245,255,0.03) 1px, transparent 1px),
                linear-gradient(rgba(0,245,255,0.03) 1px, transparent 1px);
            background-size: 50px 50px;
            pointer-events: none;
            z-index: -1;
        }

        .header {
            background: var(--bg-card);
            border-bottom: 1px solid var(--border-color);
            padding: 1rem 2rem;
            position: sticky;
            top: 0;
            z-index: 100;
        }
        .header-content {
            max-width: 1200px; margin: 0 auto;
            display: flex; align-items: center; justify-content: space-between; gap: 1rem;
        }
        .header-brand {
            display: flex; align-items: center; gap: 1rem;
            text-decoration: none; color: var(--text-primary);
        }
        .header-brand:hover { color: var(--neon-cyan); }
        .header-title {
            font-size: 1.25rem; font-weight: 600;
            background: linear-gradient(135deg, var(--neon-cyan), var(--neon-magenta));
            -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
        }
        .header-nav { display: flex; gap: 0.5rem; }
        .nav-btn {
            display: inline-flex; align-items: center; gap: 0.5rem;
            padding: 0.5rem 1rem; background: transparent;
            border: 1px solid var(--border-color); border-radius: 6px;
            color: var(--text-secondary); text-decoration: none;
            font-size: 0.875rem; transition: all 0.2s ease;
            cursor: pointer; font-family: inherit;
        }
        .nav-btn:hover:not(:disabled) { border-color: var(--neon-cyan); color: var(--neon-cyan); }
        .nav-btn:disabled { opacity: 0.4; cursor: not-allowed; }

        .layout { display: flex; max-width: 1400px; margin: 0 auto; }

        .sidebar {
            width: 280px; background: var(--bg-card);
            border-right: 1px solid var(--border-color);
            height: calc(100vh - 65px); position: sticky; top: 65px;
            overflow-y: auto; flex-shrink: 0;
        }
        .sidebar-section { padding: 1rem; }
        .sidebar-title {
            font-size: 0.75rem; text-transform: uppercase;
            letter-spacing: 0.1em; color: var(--text-secondary);
            margin-bottom: 0.75rem; padding: 0 0.5rem;
        }
        .step-link {
            display: flex; align-items: center; gap: 0.75rem;
            padding: 0.625rem 0.75rem; border-radius: 6px;
            text-decoration: none; color: var(--text-secondary);
            font-size: 0.875rem; transition: all 0.2s ease;
            margin-bottom: 0.25rem;
        }
        .step-link:hover { background: rgba(0,245,255,0.1); color: var(--text-primary); }
        .step-link.active {
            background: linear-gradient(135deg, rgba(0,245,255,0.2), rgba(255,0,255,0.2));
            color: var(--text-primary); border-left: 3px solid var(--neon-cyan);
        }
        .step-number {
            width: 24px; height: 24px; display: flex; align-items: center; justify-content: center;
            background: var(--border-color); border-radius: 6px;
            font-size: 0.75rem; font-weight: 600;
            font-family: 'JetBrains Mono', monospace; flex-shrink: 0;
        }
        .step-link.active .step-number {
            background: linear-gradient(135deg, var(--neon-cyan), var(--neon-magenta));
            color: var(--bg-dark);
        }

        .main { flex: 1; min-width: 0; padding: 2rem 3rem; }
        .content { max-width: 800px; margin: 0 auto; }

        .loading {
            display: flex; align-items: center; justify-content: center;
            height: 300px; color: var(--text-secondary);
        }
        .loading::after {
            content: ''; width: 32px; height: 32px;
            border: 3px solid var(--border-color);
            border-top-color: var(--neon-cyan); border-radius: 50%;
            animation: spin 0.8s linear infinite; margin-left: 1rem;
        }
        @keyframes spin { to { transform: rotate(360deg); } }

        .markdown h1 {
            font-size: 2.25rem; font-weight: 700; margin-bottom: 1.5rem;
            background: linear-gradient(135deg, var(--neon-cyan), var(--neon-magenta));
            -webkit-background-clip: text; -webkit-text-fill-color: transparent;
            background-clip: text; line-height: 1.3;
        }
        .markdown h2 {
            font-size: 1.5rem; font-weight: 600; margin: 2.5rem 0 1rem;
            color: var(--neon-cyan); border-bottom: 1px solid var(--border-color);
            padding-bottom: 0.5rem;
        }
        .markdown h3 { font-size: 1.25rem; font-weight: 600; margin: 2rem 0 0.75rem; color: var(--neon-magenta); }
        .markdown h4 { font-size: 1.1rem; font-weight: 600; margin: 1.5rem 0 0.5rem; color: var(--text-primary); }
        .markdown p { margin-bottom: 1rem; color: var(--text-secondary); }
        .markdown a { color: var(--neon-cyan); text-decoration: none; }
        .markdown a:hover { text-decoration: underline; }
        .markdown strong { color: var(--text-primary); font-weight: 600; }
        .markdown ul, .markdown ol { margin: 1rem 0 1.5rem 1.5rem; color: var(--text-secondary); }
        .markdown li { margin-bottom: 0.5rem; }
        .markdown li::marker { color: var(--neon-cyan); }

        .markdown input[type="checkbox"] {
            appearance: none; width: 18px; height: 18px;
            border: 2px solid var(--border-color); border-radius: 4px;
            margin-right: 0.5rem; vertical-align: middle;
            position: relative; cursor: pointer;
        }
        .markdown input[type="checkbox"]:checked { background: var(--neon-cyan); border-color: var(--neon-cyan); }
        .markdown input[type="checkbox"]:checked::after {
            content: '✓'; position: absolute; color: var(--bg-dark);
            font-size: 12px; top: 50%; left: 50%; transform: translate(-50%, -50%);
        }

        .markdown code { font-family: 'JetBrains Mono', monospace; font-size: 0.875em; }
        .markdown :not(pre) > code {
            background: var(--bg-code); padding: 0.2em 0.4em;
            border-radius: 4px; color: var(--warning-yellow);
        }
        .markdown pre {
            background: var(--bg-code); border: 1px solid var(--border-color);
            border-radius: 8px; padding: 1.25rem; overflow-x: auto; margin: 1.5rem 0;
        }
        .markdown pre code { color: var(--text-primary); background: none; padding: 0; }

        .markdown blockquote {
            background: var(--bg-card); border-left: 4px solid var(--neon-cyan);
            border-radius: 0 8px 8px 0; padding: 1rem 1.25rem; margin: 1.5rem 0;
        }
        .markdown blockquote p { margin: 0; color: var(--text-secondary); }
        .markdown blockquote p:first-child { font-weight: 600; color: var(--neon-cyan); }

        .markdown img { max-width: 100%; border-radius: 8px; border: 1px solid var(--border-color); margin: 1.5rem 0; }

        .markdown table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; }
        .markdown th, .markdown td { padding: 0.75rem 1rem; border: 1px solid var(--border-color); text-align: left; }
        .markdown th { background: var(--bg-card); color: var(--text-primary); font-weight: 600; }
        .markdown td { color: var(--text-secondary); }
        .markdown tr:hover td { background: rgba(0,245,255,0.05); }

        .markdown hr { border: none; border-top: 1px solid var(--border-color); margin: 2.5rem 0; }

        .nav-footer {
            display: flex; justify-content: space-between;
            margin-top: 3rem; padding-top: 2rem;
            border-top: 1px solid var(--border-color);
        }
        .nav-footer-btn {
            display: inline-flex; align-items: center; gap: 0.5rem;
            padding: 0.75rem 1.5rem; background: var(--bg-card);
            border: 1px solid var(--border-color); border-radius: 8px;
            color: var(--text-primary); text-decoration: none;
            font-weight: 500; transition: all 0.2s ease;
        }
        .nav-footer-btn:hover { border-color: var(--neon-cyan); transform: translateY(-2px); }
        .nav-footer-btn.disabled { opacity: 0.4; pointer-events: none; }

        @media (max-width: 900px) {
            .sidebar { display: none; }
            .main { padding: 1.5rem; }
            .header-title { display: none; }
        }