:root {
            --primary: #2c7da0;
            --primary-dark: #1e6091;
            --secondary: #61a5c2;
            --light-bg: #f8fafc;
        }.math-result{text-align:left;font-size:1.25rem}
        .integral-expression {
            font-size: 1.2rem;
            font-weight: 500;
            color: var(--primary);
            background: #eef6fc;
            padding: 10px 18px;
            border-radius: 16px;
            font-family: 'SF Mono', 'Courier New', monospace;
            word-break: break-word;
        }
        .graph-container {
            margin-top: 1.8rem;
            width: 100%;
            height: 500px;
            border-radius: 1.5rem;
            overflow: hidden;
            border: 1px solid #e9edf2;
            background: #111;
        }
        .legend-color {
            width: 20px;
            height: 20px;
            display: inline-block;
            border-radius: 4px;
            margin-right: 8px;
            vertical-align: middle;
        }
        .legend-color.surface { background: #3b82f6; }
        .legend-color.volume { background: #10b981; }
        @media (max-width: 768px) {
            .graph-container { height: 350px; }
        }