/* 导航栏样式 */
        .navbar {
            background: #3498db;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15);
            position: sticky;
            top: 0;
            z-index: 100;
        }
        
        .nav-container {
            display: flex;
            justify-content: space-between;
            align-items: center;
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
        }
        
        .logo {
            display: flex;
            align-items: center;
            color: white;
            font-weight: 700;
            font-size: 1.5rem;
            text-decoration: none;
            padding: 15px 0;
        }
        
        .logo i {
            margin-right: 10px;
            font-size: 1.8rem;
        }

.logo-icon {
  height: 40px;
  vertical-align: middle;
  margin-right: 10px;
}
        
        .nav-links {
            display: flex;
            list-style: none;
        }
        
        .nav-links li {
            margin-left: 20px;
        }
        
        .nav-links a {
            color: rgba(255, 255, 255, 0.9);
            text-decoration: none;
            font-weight: 500;
            font-size: 1.1rem;
            padding: 10px 15px;
            border-radius: 4px;
            transition: all 0.3s ease;
            position: relative;
        }
        
        .nav-links a:hover {
            color: white;
            background: rgba(255, 255, 255, 0.15);
        }
        
        .nav-links a.active {
            color: white;
            background: rgba(255, 255, 255, 0.2);
        }
        
        .nav-links a::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 50%;
            width: 0;
            height: 3px;
            background: white;
            transition: all 0.3s ease;
            transform: translateX(-50%);
        }
        
        .nav-links a:hover::after {
            width: 80%;
        }


        :root {
            --primary-color: #2e7d32;
            --primary-light: #81c784;
            --primary-lighter: #e8f5e9;
            --secondary-color: #2196f3;
            --secondary-light: #bbdefb;
            --error-color: #c62828;
            --warning-color: #ff8f00;
            --text-color: #333;
            --light-text: #757575;
            --border-radius: 12px;
            --box-shadow: 0 4px 12px rgba(0,0,0,0.1);
            --transition: all 0.3s ease;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
        }

        body {
            font-family: 'Microsoft YaHei', 'PingFang SC', sans-serif;
            line-height: 1.6;
            color: var(--text-color);
            background-color: #f9f9f9;
            padding: 20px;
            min-height: 100vh;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            background-color: white;
            border-radius: var(--border-radius);
            box-shadow: var(--box-shadow);
            overflow: hidden;
        }

        h1, h2, h3, h4 {
            color: var(--primary-color);
            margin-bottom: 1rem;
            font-weight: 600;
        }

        h1 {
            font-size: 2.2rem;
            text-align: center;
            padding: 1.5rem 0;
            background-color: var(--primary-lighter);
            border-bottom: 3px solid var(--primary-light);
        }

        h2 {
            font-size: 1.8rem;
            border-left: 5px solid var(--primary-color);
            padding-left: 1rem;
            margin-top: 2rem;
        }

        h3 {
            font-size: 1.5rem;
            color: var(--primary-color);
            margin-top: 1.5rem;
        }

        p {
            margin-bottom: 1rem;
            font-size: 1.1rem;
        }

        .control-panel {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            gap: 1.5rem;
            padding: 1.5rem;
            background-color: var(--primary-lighter);
            border-radius: var(--border-radius);
            margin: 1.5rem;
        }

        .control-group {
            display: flex;
            flex-direction: column;
        }

        label {
            font-weight: 600;
            margin-bottom: 0.5rem;
            color: var(--primary-color);
            font-size: 1.1rem;
        }

        input, select, button {
            padding: 0.8rem 1rem;
            border: 2px solid var(--primary-light);
            border-radius: var(--border-radius);
            font-size: 1.1rem;
            transition: var(--transition);
            width: 100%;
        }

        input:focus, select:focus {
            outline: none;
            border-color: var(--primary-color);
            box-shadow: 0 0 0 3px rgba(46, 125, 50, 0.2);
        }

        button {
            background-color: var(--primary-color);
            color: white;
            font-weight: 600;
            cursor: pointer;
            border: none;
            margin-top: 1rem;
        }

        button:hover {
            background-color: #388e3c;
            transform: translateY(-2px);
            box-shadow: 0 4px 8px rgba(0,0,0,0.15);
        }

        button.secondary {
            background-color: var(--secondary-color);
            width: 200px;
        }

        button.secondary:hover {
            background-color: #1976d2;
        }

        button.reset {
            background-color: var(--light-text);
        }

        button.reset:hover {
            background-color: #616161;
        }

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

        .animation-container {
            height: 400px;
            border: 3px dashed var(--primary-light);
            border-radius: var(--border-radius);
            margin: 1.5rem;
            position: relative;
            overflow: hidden;
            background-color: #f1f8e9;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .tree {
            position: absolute;
            width: 24px;
            height: 60px;
            background-color: #5d4037;
            border-radius: 4px 4px 0 0;
            transform-origin: bottom center;
            z-index: 10;
            transition: var(--transition);
        }

        .tree::after {
            content: "";
            position: absolute;
            top: -40px;
            left: -12px;
            width: 48px;
            height: 40px;
            background-color: var(--primary-color);
            border-radius: 50%;
            box-shadow: 0 4px 8px rgba(0,0,0,0.1);
        }

        .segment {
            position: absolute;
            height: 3px;
            background-color: #8d6e63;
            transform-origin: left center;
            bottom: 40px;
            z-index: 5;
        }

        .circle-segment {
            position: absolute;
            height: 3px;
            background-color: #8d6e63;
            transform-origin: center center;
            z-index: 5;
        }

        .result-panel {
            background-color: var(--primary-lighter);
            padding: 1.5rem;
            border-radius: var(--border-radius);
            margin: 1.5rem;
        }

        .formula {
            background-color: #c8e6c9;
            padding: 1.2rem;
            border-radius: var(--border-radius);
            font-family: 'Courier New', monospace;
            margin: 1rem 0;
            font-size: 1.2rem;
            border-left: 5px solid var(--primary-color);
        }

        .theory {
            margin-top: 2rem;
            background-color: var(--primary-lighter);
            padding: 1.5rem;
            border-radius: var(--border-radius);
            margin: 1.5rem;
        }

        .prediction-section {
            background-color: var(--secondary-light);
            padding: 1.5rem;
            border-radius: var(--border-radius);
            margin: 1.5rem;
        }

        .prediction-input {
            display: flex;
            gap: 1rem;
            align-items: center;
            margin-top: 1rem;
        }

        .prediction-input input {
            width: 100px;
            margin: 0;
        }

        .prediction-input button {
            margin: 0;
            flex-shrink: 0;
        }

        .circle-container {
            position: relative;
            width: 300px;
            height: 300px;
            margin: 0 auto;
        }

        .line-container {
            position: relative;
            width: 100%;
            height: 100px;
            margin-top: 60px;
        }

        #feedback {
            font-size: 1.2rem;
            padding: 0.8rem;
            border-radius: var(--border-radius);
            margin-top: 1rem;
            transition: var(--transition);
        }

        .correct {
            background-color: var(--primary-lighter);
            color: var(--primary-color);
            border: 2px solid var(--primary-light);
        }

        .incorrect {
            background-color: #ffebee;
            color: var(--error-color);
            border: 2px solid #ef9a9a;
        }

        .mode-explanation {
            margin-top: 1rem;
            padding: 1rem;
            background-color: #e3f2fd;
            border-radius: var(--border-radius);
            border-left: 5px solid var(--secondary-color);
            font-size: 1rem;
        }

        .highlight {
            background-color: #fff9c4;
            padding: 0.2rem 0.5rem;
            border-radius: 3px;
            font-weight: 600;
        }

        .button-group {
            display: flex;
            gap: 1rem;
            margin: 1.5rem;
        }

        .button-group button {
            flex: 1;
        }

        /* 响应式设计 */
        @media (max-width: 768px) {
            h1 {
                font-size: 1.8rem;
                padding: 1rem 0;
            }
            
            h2 {
                font-size: 1.5rem;
            }
            
            .control-panel {
                grid-template-columns: 1fr;
                margin: 1rem;
            }
            
            .animation-container {
                height: 300px;
                margin: 1rem;
            }
            
            .prediction-input {
                flex-direction: column;
                align-items: stretch;
            }
            
            .prediction-input input {
                width: 100%;
            }
        }

        /* 教室大屏专用样式 */
        @media (min-width: 1600px) {
            body {
                font-size: 110%;
            }
            
            h1 {
                font-size: 2.5rem;
            }
            
            .container {
                max-width: 1400px;
            }
            
            .animation-container {
                height: 500px;
            }
            
            .tree {
                width: 30px;
                height: 70px;
            }
            
            .tree::after {
                width: 54px;
                height: 45px;
                top: -45px;
                left: -12px;
            }
        }