:root {
            --light-bg: #f8fafc;
            --code-bg: #1e2a3a;
            --code-text: #e2e8f0;
        }
        body {
            font-family: 'Inter', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
            background-color: #ffffff;
            color: #1f2937;
        }
        .navbar-brand i { color: var(--primary-color); }
        .tool-card {
            background: white;
            border-radius: 20px;
            box-shadow: 0 12px 30px rgba(0,0,0,0.05);
            padding: 1.8rem;
            margin-bottom: 2rem;
            border: 1px solid #eef2f6;
            transition: box-shadow 0.2s ease;
        }
        .tool-header h1 {
            font-size: 2.2rem;
            font-weight: 700;
            letter-spacing: -0.01em;
            background: linear-gradient(135deg, #1e2a5e, #2c3e66);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
        }
        .section-title {
            font-size: 1.6rem;
            font-weight: 600;
            margin: 1.8rem 0 1rem 0;
            border-left: 5px solid var(--primary-color);
            padding-left: 1rem;
        }
        .subsection-title {
            font-weight: 600;
            margin: 1.5rem 0 0.8rem 0;
            color: var(--accent-color);
            font-size: 1.25rem;
        }
        .math-box, .info-box {
            background-color: #f1f5f9;
            border-left: 4px solid var(--primary-color);
            padding: 1.2rem;
            border-radius: 12px;
            margin: 1.5rem 0;
        }
        .flex-preview {
            background: #f9f9fb;
            border-radius: 20px;
            padding: 1.5rem;
            box-shadow: inset 0 0 0 1px rgba(0,0,0,0.05), 0 8px 20px rgba(0,0,0,0.02);
        }
        .flex-container {
            background-color: #eef2ff;
            min-height: 280px;
            border-radius: 24px;
            padding: 20px;
            display: flex;
            transition: all 0.2s ease;
            position: relative;
            border: 2px solid #cdd9ed;
            resize: both;
            overflow: auto;
        }
        .flex-item {
            background: #ffffff;
            border-radius: 16px;
            padding: 1rem 0.8rem;
            text-align: center;
            font-weight: 600;
            color: #1f2b48;
            box-shadow: 0 4px 12px rgba(0,0,0,0.08);
            border: 1px solid #dce3ec;
            min-width: 60px;
            transition: all 0.1s ease;
            font-size: 0.9rem;
        }
        .flex-item:nth-child(1) { background: #d9eff7; }
        .flex-item:nth-child(2) { background: #fef3d6; }
        .flex-item:nth-child(3) { background: #e2f5e8; }
        .flex-item:nth-child(4) { background: #ffe2e2; }
        .control-group {
            background: white;
            border-radius: 20px;
            padding: 1.2rem;
            border: 1px solid #eef2f8;
            margin-bottom: 1.2rem;
        }
        .code-block {
            background: var(--code-bg);
            border-radius: 16px;
            padding: 1.2rem;
            color: var(--code-text);
            font-family: 'Fira Code', 'Cascadia Code', monospace;
            font-size: 0.85rem;
            overflow-x: auto;
            white-space: pre-wrap;
            word-break: break-word;
        }
        .badge-prop {
            font-family: monospace;
            background: #e9ecef;
            color: #1f2b48;
            font-size: 0.7rem;
            padding: 4px 8px;
            border-radius: 30px;
        }
        .slider-label {
            font-weight: 500;
            font-size: 0.85rem;
        }
        .example-btn {
            background-color: #f1f4f9;
            border: 1px solid #cfdfed;
            border-radius: 40px;
            padding: 0.4rem 1rem;
            font-size: 0.8rem;
            transition: 0.1s;
            cursor: pointer;
        }
        .example-btn:hover {
            background-color: #e2eaf3;
            transform: translateY(-1px);
        }
        .property-table {
            width: 100%;
            border-collapse: collapse;
            margin: 1.2rem 0;
        }
        .property-table th, .property-table td {
            padding: 0.7rem;
            border: 1px solid var(--border-color);
        }
        .authority-note {
            font-size: 0.85rem;
            color: #4a627a;
            border-top: 1px solid #e2e8f0;
            padding-top: 1rem;
            margin-top: 1.5rem;
        }
        .privacy-note {
            background: #e9f4ff;
            border-radius: 16px;
            padding: 0.7rem 1.2rem;
            font-size: 0.85rem;
            margin: 1rem 0;
        }
        .footer {
            background: #f8fafc;
            margin-top: 3rem;
            padding: 2.5rem 0 1.5rem;
            border-top: 1px solid #eef2f6;
        }
        @media (max-width: 768px) {
            .tool-card { padding: 1.2rem; }
            .flex-container { min-height: 220px; }
        }