@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@400;700;900&display=swap');

        /* 基础锁定：背景不滚动，确保底部版权栏始终可见 */
        body {
            background-color: #f2f5f8;
            color: #1e293b;
            font-family: 'Noto Sans SC', sans-serif;
            margin: 0;
            overflow: hidden;
        }

        .app-shell {
            width: 100%;
            max-width: 1400px;
            margin: 0 auto;
            display: grid;
            grid-template-columns: 1fr;
            height: 100vh;
        }

        @media (min-width: 1024px) {
            .app-shell {
                grid-template-columns: 280px 1fr;
                background: #ffffff;
            }
        }

        .sidebar {
            background: #ffffff;
            padding: 40px 24px;
            display: flex;
            flex-direction: column;
            border-right: 1px solid #f1f5f9;
            height: 100vh;
        }

        .main-container {
            position: relative;
            height: 100vh;
            display: flex;
            flex-direction: column;
            background: #fbfcfd;
            overflow: hidden;
        }

        /* 主舞台：内容超长时内部滚动，不影响外部footer */
        .main-stage {
            flex: 1;
            overflow-y: auto;
            padding: 30px;
            padding-bottom: 100px;
            scroll-behavior: smooth;
        }

        .main-stage::-webkit-scrollbar {
            width: 4px;
        }

        .main-stage::-webkit-scrollbar-thumb {
            background: #e2e8f0;
            border-radius: 10px;
        }

        .fixed-footer {
            position: absolute;
            bottom: 0;
            left: 0;
            right: 0;
            background: rgba(251, 252, 253, 0.96);
            backdrop-filter: blur(10px);
            border-top: 1px solid #f1f5f9;
            padding: 20px 40px;
            z-index: 50;
        }

        .brand-icon {
            width: 54px;
            height: 54px;
            background: linear-gradient(135deg, #1d4ed8 0%, #3b82f6 100%);
            border-radius: 14px;
            display: flex;
            align-items: center;
            justify-content: center;
            box-shadow: 0 10px 20px rgba(37, 99, 235, 0.25);
            flex-shrink: 0;
        }

        .brand-icon span {
            color: white;
            font-weight: 900;
            font-size: 34px;
            line-height: 1;
        }

        .menu-item {
            transition: all 0.2s;
            cursor: pointer;
            padding: 14px;
            border-radius: 12px;
            display: flex;
            align-items: center;
            font-weight: 700;
            font-size: 14px;
            margin-bottom: 4px;
        }

        .menu-item.active {
            background-color: #eff6ff;
            color: #2563eb;
        }

        .option-tile {
            background: #ffffff;
            border: 1px solid #e2e8f0;
            border-radius: 16px;
            padding: 24px;
            cursor: pointer;
            transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
            display: flex;
            align-items: center;
            margin-bottom: 16px;
        }

        .option-tile.correct {
            border-color: #10b981;
            background: #f0fdf4;
            border-width: 2px;
        }

        .option-tile.wrong {
            border-color: #ef4444;
            background: #fef2f2;
            border-width: 2px;
        }

        .expert-panel {
            background: #ffffff;
            border-radius: 24px;
            padding: 35px;
            border: 1px solid #e2e8f0;
            margin-top: 40px;
            box-shadow: 0 20px 50px rgba(0, 0, 0, 0.04);
        }

        .shimmer {
            background: linear-gradient(90deg, #f8fafc 25%, #f1f5f9 50%, #f8fafc 75%);
            background-size: 200% 100%;
            animation: shimmerAnim 1.5s infinite;
        }

        @keyframes shimmerAnim {
            0% {
                background-position: 200% 0;
            }

            100% {
                background-position: -200% 0;
            }
        }

        /* 升级特效 */
        .level-up-overlay {
            position: fixed;
            inset: 0;
            z-index: 100;
            display: flex;
            align-items: center;
            justify-content: center;
            background: rgba(29, 78, 216, 0.95);
            backdrop-filter: blur(20px);
            opacity: 0;
            transition: opacity 0.6s ease;
            pointer-events: none;
        }

        .level-up-overlay.active {
            opacity: 1;
            pointer-events: auto;
        }

        /* 雷达图专用样式 */
        .chart-card {
            background: white;
            border-radius: 32px;
            border: 1px solid #f1f5f9;
            padding: 20px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.02);
            margin-bottom: 24px;
            position: relative;
        }

        canvas#radarChart {
            max-height: 380px !important;
            width: 100% !important;
        }

        /* 强制让诊断文本的单词间距拉大 */
        #analysis-text {
            word-spacing: 0.15em;
            letter-spacing: 0.02em;
            line-height: 1.6;
            display: block;
            white-space: pre-wrap;
            /* 保留可能存在的空格 */
        }

        /* 科目切换器基础样式 */
        .mode-selector-wrapper {
            background: rgba(248, 250, 252, 0.8);
            border: 1px solid #e2e8f0;
            border-radius: 0.75rem;
            /* 匹配 menu-item */
            padding: 0.25rem;
            display: flex;
            align-items: center;
            position: relative;
            height: 2.75rem;
        }

        /* 滑块动画 */
        #subject-slider {
            position: absolute;
            height: 2.25rem;
            width: calc(50% - 0.25rem);
            background: white;
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
            border-radius: 0.5rem;
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
            left: 0.25rem;
            z-index: 0;
        }

        /* 状态切换逻辑：当容器拥有相应类名时 */
        .mode-math #subject-slider {
            left: calc(50%);
        }

        .mode-math #text-math {
            color: #2563eb;
        }

        .mode-math #text-eng {
            color: #94a3b8;
        }

        .mode-eng #text-eng {
            color: #2563eb;
        }

        .mode-eng #text-math {
            color: #94a3b8;
        }