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

        body {
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);
            min-height: 100vh;
            padding: 20px;
            color: #2d3748;
        }

        /* 返回按钮 */
        .back-btn {
            display: inline-block;
            background: rgba(255, 255, 255, 0.2);
            color: white;
            text-decoration: none;
            padding: 10px 20px;
            border-radius: 25px;
            margin-bottom: 20px;
            font-weight: 600;
            transition: all 0.3s ease;
            backdrop-filter: blur(10px);
        }

        .back-btn:hover {
            background: rgba(255, 255, 255, 0.3);
            transform: translateY(-2px);
        }

        /* 游戏容器 */
        .game-container {
            background: rgba(255, 255, 255, 0.95);
            border-radius: 25px;
            padding: 40px;
            max-width: 900px;
            margin: 0 auto;
            box-shadow: 0 25px 50px rgba(0, 0, 0, 0.15);
            backdrop-filter: blur(10px);
            border: 2px solid rgba(255, 255, 255, 0.3);
            position: relative;
            overflow: hidden;
        }

        .game-container::before {
            content: '';
            position: absolute;
            top: -50%;
            left: -50%;
            width: 200%;
            height: 200%;
            background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
            animation: shine 3s infinite;
            pointer-events: none;
        }

        @keyframes shine {
            0% { transform: translateX(-100%) translateY(-100%) rotate(45deg); }
            50% { transform: translateX(100%) translateY(100%) rotate(45deg); }
            100% { transform: translateX(-100%) translateY(-100%) rotate(45deg); }
        }

        /* 游戏标题 */
        .game-header {
            text-align: center;
            margin-bottom: 40px;
            position: relative;
            z-index: 1;
        }

        .game-title {
            font-size: 3.2em;
            font-weight: 800;
            background: linear-gradient(45deg, #667eea, #764ba2, #f093fb);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            margin-bottom: 15px;
            text-shadow: 2px 2px 10px rgba(0, 0, 0, 0.1);
        }

        .game-subtitle {
            color: #555;
            font-size: 1.3em;
            font-weight: 500;
            margin-bottom: 20px;
        }

        /* 统计面板 */
        .quiz-stats {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
            gap: 20px;
            margin-bottom: 30px;
        }

        .stat-card {
            background: linear-gradient(135deg, #74b9ff, #0984e3);
            color: white;
            padding: 20px;
            border-radius: 15px;
            text-align: center;
            box-shadow: 0 8px 25px rgba(116, 185, 255, 0.3);
            position: relative;
            overflow: hidden;
        }

        .stat-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
            animation: statShine 2s infinite;
        }

        @keyframes statShine {
            0% { left: -100%; }
            100% { left: 100%; }
        }

        .stat-label {
            font-size: 0.9em;
            opacity: 0.9;
            margin-bottom: 8px;
        }

        .stat-value {
            font-size: 1.8em;
            font-weight: bold;
            text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.3);
        }

        /* 难度选择器 */
        .difficulty-selector {
            display: flex;
            justify-content: center;
            gap: 15px;
            margin-bottom: 30px;
            flex-wrap: wrap;
        }

        .difficulty-button {
            padding: 12px 25px;
            border: none;
            border-radius: 25px;
            font-size: 1em;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
            position: relative;
            overflow: hidden;
        }

        .difficulty-button.easy {
            background: linear-gradient(45deg, #55efc4, #00b894);
            color: white;
        }

        .difficulty-button.medium {
            background: linear-gradient(45deg, #fdcb6e, #e17055);
            color: white;
        }

        .difficulty-button.hard {
            background: linear-gradient(45deg, #fd79a8, #e84393);
            color: white;
        }

        .difficulty-button:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 30px rgba(0, 0, 0, 0.2);
        }

        .difficulty-button.active {
            transform: translateY(-3px) scale(1.05);
            box-shadow: 0 10px 35px rgba(0, 0, 0, 0.3);
        }

        /* 进度条 */
        .progress-container {
            margin: 25px 0;
            background: rgba(116, 185, 255, 0.1);
            border-radius: 10px;
            padding: 5px;
            overflow: hidden;
        }

        .progress-bar {
            height: 12px;
            background: rgba(0, 0, 0, 0.1);
            border-radius: 8px;
            overflow: hidden;
        }

        .progress-fill {
            height: 100%;
            background: linear-gradient(45deg, #74b9ff, #0984e3);
            width: 0%;
            transition: width 0.5s ease;
            border-radius: 8px;
            position: relative;
            overflow: hidden;
        }

        .progress-fill::after {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
            animation: progressShine 1.5s infinite;
        }

        @keyframes progressShine {
            0% { left: -100%; }
            100% { left: 100%; }
        }

        /* 问题卡片 */
        .question-card {
            background: linear-gradient(135deg, #f8f9fa, #ffffff);
            border-radius: 20px;
            padding: 30px;
            margin: 25px 0;
            border: 2px solid rgba(116, 185, 255, 0.2);
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
            position: relative;
        }

        .question-number {
            position: absolute;
            top: -15px;
            left: 30px;
            background: linear-gradient(45deg, #667eea, #764ba2);
            color: white;
            padding: 8px 16px;
            border-radius: 20px;
            font-size: 0.9em;
            font-weight: bold;
        }

        .question-text {
            font-size: 1.4em;
            font-weight: 600;
            color: #2d3436;
            margin: 20px 0;
            line-height: 1.6;
            text-align: center;
        }

        /* 答案网格 */
        .answers-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 20px;
            margin: 25px 0;
        }

        .answer-button {
            padding: 20px;
            background: linear-gradient(135deg, #74b9ff, #0984e3);
            color: white;
            border: none;
            border-radius: 15px;
            font-size: 1.1em;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.4s ease;
            min-height: 70px;
            display: flex;
            align-items: center;
            justify-content: center;
            text-align: center;
            position: relative;
            overflow: hidden;
            box-shadow: 0 6px 20px rgba(116, 185, 255, 0.3);
        }

        .answer-button::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
            transition: left 0.5s ease;
        }

        .answer-button:hover::before {
            left: 100%;
        }

        .answer-button:hover {
            transform: translateY(-3px);
            box-shadow: 0 10px 30px rgba(116, 185, 255, 0.4);
        }

        .answer-button.correct {
            background: linear-gradient(135deg, #00b894, #55efc4);
            animation: correctPulse 0.6s ease;
            box-shadow: 0 10px 30px rgba(0, 184, 148, 0.5);
        }

        .answer-button.wrong {
            background: linear-gradient(135deg, #e74c3c, #ff6b6b);
            animation: wrongShake 0.6s ease;
            box-shadow: 0 10px 30px rgba(231, 76, 60, 0.5);
        }

        .answer-button:disabled {
            cursor: not-allowed;
            opacity: 0.8;
        }

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

        @keyframes wrongShake {
            0%, 100% { transform: translateX(0); }
            25% { transform: translateX(-5px); }
            75% { transform: translateX(5px); }
        }

        /* 提示框 */
        .hint-box {
            background: linear-gradient(135deg, #e8f6f3, #d1f2eb);
            padding: 20px;
            border-radius: 15px;
            margin: 20px 0;
            display: none;
            border-left: 5px solid #00b894;
            box-shadow: 0 5px 15px rgba(0, 184, 148, 0.2);
            animation: slideDown 0.3s ease;
        }

        .hint-box.show {
            display: block;
        }

        @keyframes slideDown {
            from {
                opacity: 0;
                transform: translateY(-10px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        .hint-text {
            color: #00b894;
            font-style: italic;
            font-weight: 500;
            font-size: 1.1em;
        }

        /* 控制按钮 */
        .game-controls {
            display: flex;
            justify-content: center;
            gap: 15px;
            margin: 25px 0;
            flex-wrap: wrap;
        }

        .control-button {
            padding: 15px 30px;
            border: none;
            border-radius: 25px;
            font-size: 1.1em;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
            position: relative;
            overflow: hidden;
        }

        .btn-start {
            background: linear-gradient(45deg, #00b894, #55efc4);
            color: white;
        }

        .btn-hint {
            background: linear-gradient(45deg, #fdcb6e, #f39c12);
            color: white;
        }

        .btn-next {
            background: linear-gradient(45deg, #74b9ff, #0984e3);
            color: white;
        }

        .btn-restart {
            background: linear-gradient(45deg, #fd79a8, #e84393);
            color: white;
        }

        .control-button:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
        }

        /* 消息框 */
        .message {
            text-align: center;
            padding: 20px;
            border-radius: 15px;
            margin: 20px 0;
            font-weight: 600;
            font-size: 1.2em;
            display: none;
            animation: messageSlide 0.5s ease;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.1);
        }

        .message.show {
            display: block;
        }

        @keyframes messageSlide {
            from {
                opacity: 0;
                transform: scale(0.9);
            }
            to {
                opacity: 1;
                transform: scale(1);
            }
        }

        .message.correct {
            background: linear-gradient(135deg, #d1f2eb, #a7f3d0);
            color: #00b894;
            border: 2px solid #00b894;
        }

        .message.wrong {
            background: linear-gradient(135deg, #fadbd8, #f8d7da);
            color: #e74c3c;
            border: 2px solid #e74c3c;
        }

        .message.final {
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            font-size: 1.3em;
            text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.3);
        }

        /* 解释说明框 */
        .explanation {
            background: linear-gradient(135deg, #e8f6f3, #d1f2eb);
            padding: 20px;
            border-radius: 15px;
            margin-top: 15px;
            color: #00b894;
            font-weight: 600;
            border-left: 5px solid #00b894;
            animation: slideDown 0.3s ease;
        }

        /* 响应式设计 */
        @media (max-width: 768px) {
            body {
                padding: 10px;
            }

            .game-container {
                padding: 25px;
                margin: 0;
            }

            .game-title {
                font-size: 2.5em;
            }

            .quiz-stats {
                grid-template-columns: repeat(2, 1fr);
            }

            .answers-grid {
                grid-template-columns: 1fr;
            }

            .difficulty-selector {
                flex-direction: column;
                align-items: center;
            }

            .difficulty-button {
                width: 200px;
            }

            .game-controls {
                flex-direction: column;
                align-items: center;
            }

            .control-button {
                width: 200px;
            }
        }

        /* 成就徽章 */
        .achievement-badge {
            display: inline-block;
            padding: 8px 16px;
            margin: 5px;
            border-radius: 20px;
            font-size: 0.9em;
            font-weight: bold;
            animation: badgeGlow 2s infinite;
        }

        .achievement-badge.expert {
            background: linear-gradient(45deg, #f39c12, #f1c40f);
            color: white;
        }

        .achievement-badge.good {
            background: linear-gradient(45deg, #3498db, #74b9ff);
            color: white;
        }

        .achievement-badge.average {
            background: linear-gradient(45deg, #95a5a6, #bdc3c7);
            color: white;
        }

        @keyframes badgeGlow {
            0%, 100% { box-shadow: 0 0 5px rgba(0, 0, 0, 0.2); }
            50% { box-shadow: 0 0 20px rgba(255, 255, 255, 0.5); }
        }