:root {
            --primary: #2962ff;
            --secondary: #0039cb;
            --background: #f5f7ff;
            --dark: #1e1e2f;
            --light: #ffffff;
            --success: #00bfa6;
            --accent: #ff1744;
        }
        
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'SimSun', '宋体', serif;
            background-color: var(--background);
            color: var(--dark);
            min-height: 100vh;
            padding: 20px;
            line-height: 1.6;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
            border-radius: 12px;
            overflow: hidden;
            background: var(--light);
        }

        .header {
            background: linear-gradient(135deg, var(--primary), var(--secondary));
            color: white;
            padding: 30px;
            text-align: center;
        }

        .header h1 {
            font-size: 32px;
            margin-bottom: 10px;
            font-weight: 700;
        }

        .header p {
            font-size: 20px;
            opacity: 0.9;
        }

        .main-content {
            padding: 40px;
        }

        .visualization-area {
            background: #f8f9fa;
            border-radius: 15px;
            padding: 30px;
            margin-bottom: 30px;
            min-height: 650px;
            position: relative;
            border: 2px solid #e9ecef;
        }

        .svg-container {
            width: 100%;
            height: 600px;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .svg-container svg {
            background: white;
            border-radius: 8px;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
        }

        .grid-line {
            stroke: #e0e0e0;
            stroke-width: 0.5;
        }

        .grid-line-major {
            stroke: #bdbdbd;
            stroke-width: 1;
        }

        .controls {
            display: flex;
            justify-content: center;
            gap: 15px;
            margin-bottom: 30px;
            flex-wrap: wrap;
        }

        .btn {
            padding: 12px 24px;
            border: none;
            border-radius: 25px;
            font-size: 18px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            text-transform: uppercase;
            letter-spacing: 1px;
            font-family: 'SimSun', '宋体', serif;
        }

        .btn-primary {
            background: linear-gradient(135deg, #3b82f6, #1d4ed8);
            color: white;
            border: none;
        }

        .btn-secondary {
            background: linear-gradient(135deg, #10b981, #059669);
            color: white;
            border: none;
        }

        .btn-success {
            background: linear-gradient(135deg, #f59e0b, #d97706);
            color: white;
            border: none;
        }

        .btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 10px 20px rgba(0,0,0,0.2);
        }

        .step-info {
            background: white;
            border-radius: 12px;
            padding: 25px;
            box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
            border: 1px solid #e5e7eb;
            border-left: 4px solid #3b82f6;
        }

        .step-title {
            font-size: 24px;
            color: #3b82f6;
            margin-bottom: 10px;
            font-weight: 700;
        }

        .step-description {
            font-size: 18px;
            line-height: 1.6;
            color: #374151;
        }

        .formula-display {
            background: linear-gradient(135deg, #dbeafe, #bfdbfe);
            color: #1e40af;
            border: 2px solid #93c5fd;
            padding: 20px;
            border-radius: 12px;
            text-align: center;
            font-size: 24px;
            font-weight: 600;
            margin-top: 20px;
            box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
        }

        .progress-bar {
            width: 100%;
            height: 8px;
            background: #e9ecef;
            border-radius: 4px;
            margin: 20px 0;
            overflow: hidden;
        }

        .progress-fill {
            height: 100%;
            background: linear-gradient(90deg, #1976d2, #2196f3);
            border-radius: 4px;
            transition: width 0.5s ease;
            width: 0%;
        }

        .parallelogram {
            fill: rgba(59, 130, 246, 0.7);
            stroke: #3b82f6;
            stroke-width: 3;
            transition: all 0.5s ease;
        }

        .triangle {
            fill: rgba(245, 158, 11, 0.8);
            stroke: #f59e0b;
            stroke-width: 3;
            transition: all 1.2s cubic-bezier(0.4, 0, 0.2, 1);
        }

        .triangle-moving {
            fill: rgba(245, 158, 11, 0.9);
            stroke: #f59e0b;
            stroke-width: 3;
            transition: transform 2.5s cubic-bezier(0.25, 0.46, 0.45, 0.94);
        }

        .rectangle {
            fill: rgba(16, 185, 129, 0.7);
            stroke: #10b981;
            stroke-width: 3;
            transition: all 0.5s ease;
        }

        .cut-line {
            stroke: #f44336;
            stroke-width: 3;
            stroke-dasharray: 8,4;
            opacity: 0;
            transition: opacity 0.8s ease;
        }

        .dimension-text {
            font-family: 'SimSun', '宋体', serif;
            font-size: 20px;
            font-weight: 600;
            fill: #1f2937;
            text-anchor: middle;
        }

        .parameter-controls {
            background: white;
            border-radius: 15px;
            padding: 20px;
            margin-bottom: 20px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }

        .param-slider {
            width: 100%;
            height: 6px;
            background: #e9ecef;
            border-radius: 3px;
            outline: none;
            -webkit-appearance: none;
            -moz-appearance: none;
            appearance: none;
            cursor: pointer;
            margin: 8px 0;
        }

        .param-slider::-webkit-slider-thumb {
            -webkit-appearance: none;
            -moz-appearance: none;
            appearance: none;
            width: 18px;
            height: 18px;
            border-radius: 50%;
            background: linear-gradient(135deg, #3b82f6, #1d4ed8);
            cursor: pointer;
            box-shadow: 0 2px 6px rgba(59, 130, 246, 0.3);
            transition: all 0.3s ease;
        }

        .param-slider::-webkit-slider-thumb:hover {
            transform: scale(1.2);
            box-shadow: 0 4px 12px rgba(25, 118, 210, 0.4);
        }

        .param-group {
            text-align: center;
            padding: 10px;
            background: #f8f9fa;
            border-radius: 8px;
        }

        .footer {
            background: linear-gradient(to right, #2c3e50, #1a2530);
            color: #ecf0f1;
            text-align: center;
            padding: 20px;
            margin-top: 25px;
            border-radius: 0 0 10px 10px;
        }

        @media (max-width: 768px) {
            .header h1 {
                font-size: 28px;
            }
            
            .main-content {
                padding: 20px;
            }
            
            .controls {
                flex-direction: column;
                align-items: center;
            }
            
            .btn {
                width: 200px;
            }
            
            .parameter-controls div[style*="grid-template-columns"] {
                grid-template-columns: 1fr !important;
                gap: 15px !important;
            }
            
            .param-group {
                margin-bottom: 10px;
            }
        }