body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background-color: #f8fafc;
        }
        
        .captcha-card {
            transition: transform 0.3s ease, box-shadow 0.3s ease;
        }
        
        .captcha-card:hover {
            transform: translateY(-2px);
            box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
        }
        
        .btn {
            transition: all 0.2s ease;
        }
        
        .btn:hover:not(:disabled) {
            transform: translateY(-1px);
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
        }
        
        .btn:active:not(:disabled) {
            transform: translateY(0);
        }
        
        .input-field {
            transition: border-color 0.2s ease, box-shadow 0.2s ease;
        }
        
        .input-field:focus {
            border-color: #3b82f6;
            box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.25);
        }
        
        /* 加载动画 */
        .spinner {
            border: 3px solid rgba(255, 255, 255, 0.3);
            border-radius: 50%;
            border-top: 3px solid white;
            width: 20px;
            height: 20px;
            animation: spin 1s linear infinite;
        }
        
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        
        /* 错误消息动画 */
        .error-message {
            animation: slideDown 0.3s ease;
        }
        
        @keyframes slideDown {
            from { opacity: 0; transform: translateY(-10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        
        /* 标题动画 */
        .title {
            animation: fadeIn 0.5s ease;
        }
        
        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }