    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Microsoft YaHei', Arial, sans-serif;
            background: linear-gradient(135deg, #0a0e27 0%, #1a1f3a 100%);
            color: #ffffff;
            overflow: hidden;
        }

        .app-container {
            display: flex;
            height: 100vh;
        }

        .sidebar {
            width: 350px;
            background: rgba(255, 255, 255, 0.05);
            backdrop-filter: blur(10px);
            border-right: 1px solid rgba(255, 255, 255, 0.1);
            padding: 20px;
            overflow-y: auto;
        }

        .app-header {
            text-align: center;
            margin-bottom: 30px;
            padding-bottom: 20px;
            border-bottom: 1px solid rgba(255, 255, 255, 0.1);
        }

        .app-title {
            font-size: 24px;
            color: #64b5f6;
            margin-bottom: 8px;
        }

        .app-subtitle {
            font-size: 14px;
            color: #cccccc;
            margin-bottom: 20px;
        }

        .control-section {
            background: rgba(255, 255, 255, 0.05);
            border: 1px solid rgba(255, 255, 255, 0.1);
            border-radius: 12px;
            padding: 20px;
            margin-bottom: 20px;
        }

        .section-title {
            font-size: 16px;
            color: #64b5f6;
            margin-bottom: 15px;
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .dimension-control {
            margin-bottom: 15px;
        }

        .dimension-label {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 8px;
            font-size: 14px;
        }

        .dimension-value {
            color: #64b5f6;
            font-weight: bold;
        }

        .dimension-slider {
            width: 100%;
            height: 6px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 3px;
            outline: none;
            -webkit-appearance: none;
        }

        .dimension-slider::-webkit-slider-thumb {
            -webkit-appearance: none;
            width: 18px;
            height: 18px;
            background: #64b5f6;
            border-radius: 50%;
            cursor: pointer;
        }

        .color-control {
            margin-bottom: 15px;
        }

        .color-options {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 8px;
            margin-top: 10px;
        }

        .color-option {
            width: 40px;
            height: 40px;
            border-radius: 8px;
            border: 2px solid rgba(255, 255, 255, 0.2);
            cursor: pointer;
            transition: all 0.3s ease;
            position: relative;
        }

        .color-option:hover {
            transform: scale(1.1);
            border-color: rgba(255, 255, 255, 0.5);
        }

        .color-option.selected {
            border-color: #64b5f6;
            border-width: 3px;
            transform: scale(1.1);
        }

        .color-option.selected::after {
            content: '✓';
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            color: white;
            font-weight: bold;
            font-size: 16px;
            text-shadow: 1px 1px 2px rgba(0,0,0,0.8);
        }

        .action-buttons {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 10px;
            margin-bottom: 15px;
        }

        .btn {
            padding: 12px 16px;
            border: none;
            border-radius: 8px;
            font-size: 14px;
            cursor: pointer;
            transition: all 0.3s ease;
            font-weight: 500;
        }

        .btn-primary {
            background: linear-gradient(135deg, #64b5f6, #42a5f5);
            color: white;
        }

        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 4px 12px rgba(100, 181, 246, 0.3);
        }

        .btn-secondary {
            background: rgba(255, 255, 255, 0.1);
            color: #ffffff;
            border: 1px solid rgba(255, 255, 255, 0.2);
        }

        .btn-secondary:hover {
            background: rgba(255, 255, 255, 0.15);
        }

        .btn-full {
            grid-column: 1 / -1;
        }

        .formula-section {
            background: rgba(255, 193, 7, 0.1);
            border: 1px solid rgba(255, 193, 7, 0.3);
            border-radius: 8px;
            overflow: hidden;
            transition: all 0.3s ease;
        }

        .formula-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 15px;
            background: rgba(255, 193, 7, 0.15);
            cursor: pointer;
            transition: background 0.3s ease;
        }

        .formula-header:hover {
            background: rgba(255, 193, 7, 0.2);
        }

        .formula-title {
            font-size: 16px;
            color: #ffc107;
            font-weight: bold;
        }

        .toggle-icon {
            font-size: 16px;
            color: #ffc107;
            transition: transform 0.3s ease;
        }

        .toggle-icon.collapsed {
            transform: rotate(-90deg);
        }

        .formula-content {
            padding: 15px;
            text-align: center;
            transition: all 0.3s ease;
            max-height: 200px;
            overflow: hidden;
        }

        .formula-content.hidden {
            max-height: 0;
            padding: 0 15px;
        }

        .formula-text {
            font-size: 18px;
            color: #ffc107;
            font-weight: bold;
            margin-bottom: 8px;
        }

        .formula-calculation {
            font-size: 14px;
            color: #cccccc;
        }

        .main-area {
            flex: 1;
            position: relative;
        }

        .viewport {
            width: 100%;
            height: 100%;
            position: relative;
        }

        #three-canvas {
            width: 100%;
            height: 100%;
        }

        .viewport-overlay {
            position: absolute;
            top: 20px;
            left: 20px;
            background: rgba(0, 0, 0, 0.7);
            backdrop-filter: blur(10px);
            border-radius: 8px;
            padding: 15px;
            max-width: 300px;
        }

        .current-step {
            font-size: 16px;
            color: #64b5f6;
            font-weight: bold;
            margin-bottom: 8px;
        }

        .step-status {
            font-size: 14px;
            color: #cccccc;
            line-height: 1.4;
        }

        .controls-guide {
            position: absolute;
            bottom: 20px;
            right: 20px;
            background: rgba(0, 0, 0, 0.7);
            backdrop-filter: blur(10px);
            border-radius: 8px;
            padding: 15px;
        }

        .guide-title {
            font-size: 14px;
            color: #64b5f6;
            margin-bottom: 10px;
            font-weight: bold;
        }

        .control-item {
            display: flex;
            align-items: center;
            gap: 8px;
            margin-bottom: 6px;
            font-size: 12px;
            color: #cccccc;
        }

        .control-item:last-child {
            margin-bottom: 0;
        }

        .control-icon {
            font-size: 14px;
        }

        .footer {
            background: linear-gradient(to right);
            color: #0c0302;
            text-align: center;
            padding: 10px;
            margin-top: 15px;
            border-radius: 0 0 10px 10px;
        }

        .notification {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background: rgba(100, 181, 246, 0.9);
            color: white;
            padding: 20px 30px;
            border-radius: 12px;
            font-size: 16px;
            font-weight: bold;
            z-index: 1000;
            opacity: 0;
            pointer-events: none;
            transition: all 0.3s ease;
        }

        .teaching-highlight {
            background: linear-gradient(135deg, #ffc107, #ff9800) !important;
            color: #000 !important;
            font-size: 20px !important;
            padding: 25px 35px !important;
            box-shadow: 0 8px 32px rgba(255, 193, 7, 0.4);
            border: 2px solid #ffc107;
        }

        @keyframes pulse {
            0%, 100% { transform: translate(-50%, -50%) scale(1); }
            50% { transform: translate(-50%, -50%) scale(1.05); }
        }

        .pulse {
            animation: pulse 2s infinite;
        }

        @keyframes bounce {
            0%, 20%, 50%, 80%, 100% { transform: translate(-50%, -50%) translateY(0); }
            40% { transform: translate(-50%, -50%) translateY(-10px); }
            60% { transform: translate(-50%, -50%) translateY(-5px); }
        }

        .bounce {
            animation: bounce 1s ease-in-out;
        }
