.ruler-canvas {
            width: 100%;
            background: #ffffff;
            border: 2px solid #2c3e50;
            border-radius: 12px;
            cursor: crosshair;
            box-shadow: 0 4px 12px rgba(0,0,0,0.1);
            margin-top: 1rem;
            background: #fefefe;
        }
        .calibration-panel {
            background: #f0f4fa;
            border-radius: 16px;
            padding: 1rem;
            margin: 1rem 0;
        }
        .calibration-slider {
            width: 100%;
            margin: 10px 0;
        }
        .reference-line {
            background: #ffc107;
            height: 24px;
            width: 100%;
            position: relative;
            border-radius: 12px;
            margin: 10px 0;
        }
        .reference-line span {
            position: absolute;
            right: 8px;
            top: -20px;
            font-size: 0.8rem;
            font-weight: bold;
            background: white;
            padding: 0 6px;
            border-radius: 12px;
        }
        .badge-cal {
            font-family: monospace;
            background: #2c3e50;
            color: white;
        }
        .step-guide {
            background: #f2f5f9;
            border-left: 4px solid #3498db;
        }
        .legend-ruler i {
            font-size: 1rem;
        }
        .btn-outline-accent {
            border-color: #2c7da0;
            color: #2c7da0;
        }
        .btn-outline-accent:hover {
            background: #2c7da0;
            color: white;
        }