:root {
            --primary-color: #4ecdc4;
            --secondary-color: #45b7d1;
            --accent-color: #ff6b35;
            --success-color: #96ceb4;
            --warning-color: #ffeaa7;
            --error-color: #ff6b6b;
            --text-color: #2d3436;
            --bg-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            --card-shadow: 0 10px 30px rgba(0,0,0,0.2);
        }

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

        body {
            font-family: 'Comic Sans MS', cursive, sans-serif;
            background: var(--bg-gradient);
            min-height: 100vh;
            overflow-x: hidden;
            display: flex;
            flex-direction: column;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
            flex: 1;
        }

        /* 头部logo */
        .header {
            text-align: center;
            padding: 20px 0;
            color: white;
        }

        .logo {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 15px;
            margin-bottom: 10px;
        }

        .logo-icon {
            font-size: 3rem;
            animation: logoSpin 5s linear infinite;
        }

        @keyframes logoSpin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }

        .logo-text {
            font-size: 2.5rem;
            font-weight: bold;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        /* 欢迎界面 */
        .welcome-screen {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            min-height: 70vh;
            text-align: center;
            color: white;
        }

        .title {
            font-size: 3.5rem;
            font-weight: bold;
            margin-bottom: 2rem;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
            animation: titleBounce 2s ease-in-out infinite alternate;
        }

        @keyframes titleBounce {
            0% { transform: translateY(0px); }
            100% { transform: translateY(-10px); }
        }

        .subtitle {
            font-size: 1.5rem;
            margin-bottom: 3rem;
            opacity: 0.9;
        }

        .start-btn {
            background: var(--accent-color);
            color: white;
            border: none;
            padding: 20px 40px;
            font-size: 1.5rem;
            border-radius: 50px;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: var(--card-shadow);
            animation: pulse 2s infinite;
        }

        @keyframes pulse {
            0% { transform: scale(1); }
            50% { transform: scale(1.05); }
            100% { transform: scale(1); }
        }

        .start-btn:hover {
            transform: translateY(-5px);
            box-shadow: 0 15px 40px rgba(0,0,0,0.3);
        }

        /* 游戏模式选择 */
        .mode-selection {
            display: none;
            text-align: center;
            color: white;
            padding: 2rem 0;
        }

        .mode-title {
            font-size: 2.5rem;
            margin-bottom: 3rem;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .mode-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
            gap: 2rem;
            margin-bottom: 2rem;
        }

        .mode-card {
            background: rgba(255,255,255,0.1);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            padding: 2rem;
            cursor: pointer;
            transition: all 0.3s ease;
            border: 2px solid rgba(255,255,255,0.2);
        }

        .mode-card:hover {
            transform: translateY(-10px);
            background: rgba(255,255,255,0.2);
            box-shadow: 0 20px 40px rgba(0,0,0,0.3);
        }

        .mode-icon {
            font-size: 4rem;
            margin-bottom: 1rem;
            display: block;
        }

        .mode-name {
            font-size: 1.5rem;
            font-weight: bold;
            margin-bottom: 1rem;
        }

        .mode-desc {
            font-size: 1rem;
            opacity: 0.9;
            line-height: 1.5;
        }

        /* 游戏界面 */
        .game-screen {
            display: none;
            color: white;
        }

        .game-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 2rem;
            flex-wrap: wrap;
            gap: 1rem;
        }

        .score-board {
            display: flex;
            gap: 2rem;
            align-items: center;
        }

        .score-item {
            background: rgba(255,255,255,0.1);
            padding: 10px 20px;
            border-radius: 25px;
            backdrop-filter: blur(10px);
            font-weight: bold;
        }

        .back-btn {
            background: var(--error-color);
            color: white;
            border: none;
            padding: 10px 20px;
            border-radius: 25px;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        .back-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0,0,0,0.3);
        }

        /* 口诀接龙模式 */
        .quiz-container {
            background: rgba(255,255,255,0.1);
            backdrop-filter: blur(15px);
            border-radius: 20px;
            padding: 3rem;
            text-align: center;
            margin-bottom: 2rem;
        }

        .question {
            font-size: 3rem;
            font-weight: bold;
            margin-bottom: 2rem;
            color: var(--warning-color);
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .options {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 1rem;
            margin-bottom: 2rem;
        }

        .option-btn {
            background: var(--primary-color);
            color: white;
            border: none;
            padding: 20px;
            font-size: 1.5rem;
            border-radius: 15px;
            cursor: pointer;
            transition: all 0.3s ease;
            font-weight: bold;
        }

        .option-btn:hover {
            transform: translateY(-5px);
            box-shadow: 0 10px 25px rgba(0,0,0,0.3);
        }

        .option-btn.correct {
            background: var(--success-color);
            animation: correctAnswer 0.6s ease;
        }

        .option-btn.wrong {
            background: var(--error-color);
            animation: wrongAnswer 0.6s ease;
        }

        @keyframes correctAnswer {
            0% { transform: scale(1); }
            50% { transform: scale(1.1); }
            100% { transform: scale(1); }
        }

        @keyframes wrongAnswer {
            0% { transform: translateX(0); }
            25% { transform: translateX(-10px); }
            75% { transform: translateX(10px); }
            100% { transform: translateX(0); }
        }

        /* 速算竞技场 */
        .timer-container {
            text-align: center;
            margin-bottom: 2rem;
        }

        .timer {
            font-size: 3rem;
            font-weight: bold;
            color: var(--warning-color);
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .timer.warning {
            color: var(--error-color);
            animation: timerWarning 1s infinite;
        }

        @keyframes timerWarning {
            0% { transform: scale(1); }
            50% { transform: scale(1.1); }
            100% { transform: scale(1); }
        }

        .combo {
            position: fixed;
            top: 20px;
            right: 20px;
            background: var(--accent-color);
            color: white;
            padding: 10px 20px;
            border-radius: 25px;
            font-weight: bold;
            font-size: 1.2rem;
            animation: comboEffect 0.5s ease;
            z-index: 1000;
        }

        @keyframes comboEffect {
            0% { transform: scale(0.8); opacity: 0; }
            50% { transform: scale(1.2); }
            100% { transform: scale(1); opacity: 1; }
        }

        /* 填空模式 */
        .fill-blank-container {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 2rem;
        }

        .equation {
            font-size: 4rem;
            font-weight: bold;
            display: flex;
            align-items: center;
            gap: 1rem;
            color: white;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .blank {
            width: 100px;
            height: 80px;
            border: 3px dashed var(--warning-color);
            border-radius: 15px;
            display: flex;
            align-items: center;
            justify-content: center;
            background: rgba(255,255,255,0.1);
            font-size: 3rem;
            color: var(--warning-color);
            transition: all 0.3s ease;
        }

        .blank.filled {
            background: var(--success-color);
            border-color: var(--success-color);
            color: white;
        }

        .number-options {
            display: flex;
            gap: 1rem;
            flex-wrap: wrap;
            justify-content: center;
        }

        .number-btn {
            width: 60px;
            height: 60px;
            background: var(--primary-color);
            color: white;
            border: none;
            border-radius: 50%;
            font-size: 1.5rem;
            font-weight: bold;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        .number-btn:hover {
            transform: scale(1.1);
            background: var(--secondary-color);
        }

        .number-btn.used {
            opacity: 0.5;
            cursor: not-allowed;
        }

        /* 结果弹窗 */
        .result-modal {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0,0,0,0.8);
            display: none;
            align-items: center;
            justify-content: center;
            z-index: 2000;
        }

        .result-content {
            background: white;
            padding: 3rem;
            border-radius: 20px;
            text-align: center;
            max-width: 400px;
            width: 90%;
            animation: modalAppear 0.5s ease;
        }

        @keyframes modalAppear {
            0% { transform: scale(0.8); opacity: 0; }
            100% { transform: scale(1); opacity: 1; }
        }

        .result-icon {
            font-size: 5rem;
            margin-bottom: 1rem;
        }

        .result-title {
            font-size: 2rem;
            font-weight: bold;
            margin-bottom: 1rem;
            color: var(--text-color);
        }

        .result-score {
            font-size: 1.5rem;
            margin-bottom: 2rem;
            color: var(--text-color);
        }

        .result-btn {
            background: var(--primary-color);
            color: white;
            border: none;
            padding: 15px 30px;
            font-size: 1.2rem;
            border-radius: 25px;
            cursor: pointer;
            margin: 0 10px;
            transition: all 0.3s ease;
        }

        .result-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(0,0,0,0.3);
        }

        /* 粒子效果 */
        .particle {
            position: fixed;
            pointer-events: none;
            z-index: 1500;
        }

        /* 底部信息 */
        .footer {
            text-align: center;
            color: white;
            padding: 20px;
            background: rgba(0,0,0,0.1);
            backdrop-filter: blur(5px);
            margin-top: auto;
        }

        .footer p {
            margin: 5px 0;
            font-size: 1rem;
        }

        /* 响应式设计 */
        @media (max-width: 768px) {
            .title {
                font-size: 2.5rem;
            }
            
            .logo-text {
                font-size: 1.8rem;
            }
            
            .logo-icon {
                font-size: 2rem;
            }
            
            .mode-grid {
                grid-template-columns: 1fr;
            }
            
            .question {
                font-size: 2rem;
            }
            
            .equation {
                font-size: 2.5rem;
                flex-direction: column;
                gap: 1rem;
            }
            
            .game-header {
                flex-direction: column;
                text-align: center;
            }
        }

        @media (max-width: 480px) {
            .container {
                padding: 10px;
            }
            
            .quiz-container {
                padding: 1.5rem;
            }
            
            .options {
                grid-template-columns: 1fr;
            }
        }