/* 年级分组 */
.grade-group {
    margin-bottom: 2px;
}

/* 目录交互行使用原生按钮，并清除浏览器默认按钮外观。 */
.grade-header,
.chapter-header,
.ggb-item {
    width: 100%;
    appearance: none;
    font: inherit;
    text-align: left;
}

/* 年级标题 - 独立方块 + 左侧色块 */
.grade-header {
    display: flex;
    align-items: center;
    padding: 0.5rem 0.75rem;
    background: white;
    border: 0.5px solid #333;
    border-left: 6px solid var(--primary-color, #4a6fa5);
    border-radius: 4px;
    cursor: pointer;
    transition: color 0.2s ease, background-color 0.2s ease,
        border-color 0.2s ease, box-shadow 0.2s ease;
    margin-bottom: 0;
    /* 展开后固定在侧边栏顶部。 */
    position: sticky;
    top: 0;
    z-index: 10;
}

/* 主目录循环配色 */
.grade-group:nth-child(6n+1)>.grade-header {
    border-left-color: #4a6fa5;
}

.grade-group:nth-child(6n+2)>.grade-header {
    border-left-color: #0d9488;
}

.grade-group:nth-child(6n+3)>.grade-header {
    border-left-color: #d97706;
}

.grade-group:nth-child(6n+4)>.grade-header {
    border-left-color: #7c3aed;
}

.grade-group:nth-child(6n+5)>.grade-header {
    border-left-color: #16a34a;
}

.grade-group:nth-child(6n+6)>.grade-header {
    border-left-color: #e11d48;
}

.grade-header:hover {
    background: #f0f7ff;
}

/* 激活时：蓝色背景 + 白色文字 */
.grade-header.expanded {
    background: #6b8db5;
    color: white;
    border-left-width: 6px;
}

.grade-header.expanded .grade-name,
.grade-header.expanded .grade-toggle,
.grade-header.expanded .chapter-count {
    color: white;
}

/* 从购买弹窗直达目录时，用约 3 秒的柔和蓝色呼吸光提示目标行。 */
.grade-header.resource-route-attention {
    animation: resource-route-attention 0.8s ease-in-out 4;
}

@keyframes resource-route-attention {
    0%,
    100% {
        box-shadow: 0 0 0 0 rgba(37, 99, 235, 0),
            0 0 0 rgba(37, 99, 235, 0);
    }

    50% {
        background: #2563eb;
        border-color: #1d4ed8;
        box-shadow: 0 0 0 5px rgba(37, 99, 235, 0.18),
            0 10px 24px rgba(37, 99, 235, 0.24);
    }
}

.grade-icon {
    font-size: 1rem;
    margin-right: 0.5rem;
}

/* 年级名称 */
.grade-name {
    flex: 1;
    font-weight: 500;
    color: #000000;
    font-size: 0.95rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.grade-toggle {
    color: #475569;
    font-size: 0.6rem;
    transition: transform 0.3s ease;
    flex-shrink: 0;
}

.grade-header.expanded .grade-toggle {
    transform: rotate(90deg);
}

/* 章节列表 */
.chapter-list {
    display: none;
    padding-left: 10px;
    margin-top: 0;
    margin-left: 4px;
}

.chapter-list.show {
    display: block;
    border-left: 1px dashed #333;
}

.chapter-item {
    margin-bottom: 0;
}

/* 深层嵌套目录样式优化 */
.ggb-list .chapter-item {
    margin-left: 0 !important;
}

.ggb-list .ggb-list {
    padding-left: 8px;
    margin-left: 4px;
}

.ggb-list .ggb-list.show {
    border-left: 1px dashed #333;
}

.ggb-list .ggb-list .ggb-list {
    padding-left: 6px;
}

.ggb-list .ggb-list .ggb-list .ggb-list {
    padding-left: 4px;
}

.ggb-list .ggb-list .ggb-list .ggb-list .ggb-list {
    padding-left: 4px;
}

/* 章节标题 - 独立方块 */
.chapter-header {
    display: flex;
    align-items: center;
    padding: 0.45rem 0.75rem;
    color: #000000;
    cursor: pointer;
    background: white;
    border: 0.5px solid #333;
    border-radius: 4px;
    margin-top: 2px;
    transition: color 0.15s ease, background-color 0.15s ease,
        border-color 0.15s ease, box-shadow 0.15s ease;
    font-size: 0.88rem;
    min-height: 26px;
    overflow: hidden;
    gap: 0.25rem;
    /* 子文件夹标题保持在当前目录顶部。 */
    position: sticky;
    top: 2.4rem;
    z-index: 5;
}

.chapter-header span:not(.chapter-toggle):not(.chapter-icon):not(.chapter-count) {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    min-width: 0;
}

.chapter-icon {
    font-size: 0.7rem;
    flex-shrink: 0;
    margin-right: 0.3rem;
}

.chapter-header:hover {
    background: #f0f7ff;
    color: var(--text-primary);
}

/* 激活时：蓝色背景 + 白色文字 */
.chapter-header.expanded {
    background: #6b8db5;
    color: white;
    font-weight: 500;
}

.chapter-header.expanded span,
.chapter-header.expanded .chapter-icon,
.chapter-header.expanded .chapter-toggle {
    color: white;
}

.chapter-toggle {
    margin-left: auto;
    font-size: 0.6rem;
    transition: transform 0.3s ease;
}

/* 课件数量标签 - 靠右显示 */
.chapter-count {
    margin-left: auto;
    font-size: 0.8em;
    color: #000;
    white-space: nowrap;
    flex-shrink: 0;
}

/* 有三角形时，数量不需要再次使用 margin-left: auto。 */
.chapter-count + .chapter-toggle {
    margin-left: 8px;
}

.chapter-header.expanded .chapter-toggle {
    transform: rotate(90deg);
}

/* 课件列表 */
.ggb-list {
    display: none;
    padding-left: 8px;
    margin-top: 0;
    margin-left: 4px;
}

.ggb-list.show {
    display: block;
    border-left: 1px dashed #333;
}

/* 课件项 - 独立方块 */
.ggb-item {
    display: flex;
    align-items: center;
    padding: 0.4rem 0.75rem;
    color: var(--text-secondary);
    cursor: pointer;
    background: white;
    border: 0.5px solid #333;
    border-radius: 4px;
    margin-top: 2px;
    transition: color 0.15s ease, background-color 0.15s ease,
        border-color 0.15s ease, box-shadow 0.15s ease;
    font-size: 0.88rem;
}

.ggb-item:hover {
    background: #f0f7ff;
    color: var(--text-primary);
}

/* 选中的课件：蓝色背景 */
.ggb-item.active {
    background: #6b8db5;
    color: white;
}

.ggb-item-icon {
    margin-right: 0.4rem;
}

/* 右侧内容区：限制高度，让子元素能正确布局。 */
.content-area {
    flex: 1;
    padding: 0;
    background: var(--page-bg, #f5f7fa);
    overflow: hidden;
    display: flex;
    flex-direction: column;
    min-width: 0;
    min-height: 0;
    max-height: 100%;
    position: relative;
    /* 限制最大高度。 */
}

/* 欢迎面板 */
.welcome-panel {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    text-align: center;
    padding: 3rem;
}

.welcome-icon {
    font-size: 4rem;
    margin-bottom: 1.5rem;
}

.welcome-panel h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.welcome-panel>p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.welcome-features {
    display: flex;
    gap: 2rem;
    flex-wrap: wrap;
    justify-content: center;
}

.welcome-feature {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.25rem;
    background: var(--bg-light);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
}

/* GGB 展示面板 */
.ggb-panel {
    background: var(--bg-white);
    border-radius: 0;
    box-shadow: none;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    flex: 1;
    min-height: 0;
    /* 关键：允许 flex 子元素收缩。 */
    max-height: 100%;
}

.ggb-header {
    padding: 0 16px;
    min-height: 60px;
    background: linear-gradient(135deg, var(--subject-color, var(--primary-color)) 0%, var(--subject-dark, var(--primary-dark)) 100%);
    color: white;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-shrink: 0;
    flex-wrap: wrap;
}

.ggb-header-left h3 {
    font-size: 1rem;
    margin: 0;
}

.ggb-path {
    display: none;
}

.ggb-header-right {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.ggb-header-right button:not(.rotate-fullscreen-btn) {
    height: 32px;
    padding: 0 0.75rem;
    font-size: 0.8rem;
    display: inline-flex;
    align-items: center;
    box-sizing: border-box;
}

/* 全屏按钮和下载按钮 */
.fullscreen-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: var(--radius-md);
    color: white;
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
}

.fullscreen-btn:hover {
    background: rgba(255, 255, 255, 0.3);
}

#download-btn {
    background: rgba(34, 197, 94, 0.3);
    border-color: rgba(34, 197, 94, 0.5);
}

#download-btn:hover {
    background: rgba(34, 197, 94, 0.5);
}

/* GGB 展示区域 */
.ggb-display-area {
    flex: 1;
    position: relative;
    background: var(--bg-light);
    overflow: hidden;
    overscroll-behavior: contain;
    min-height: 0;
    min-width: 0;
    /* 尺寸由 JavaScript 动态计算。 */
}

/* 独立的 GGB 展示窗口 */
.ggb-display-window {
    position: absolute;
    top: 0;
    left: 0;
    background: white;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    /* 位置和尺寸完全由 JavaScript 控制。 */
}

.ggb-display-area.ggb-applet-loading .ggb-display-window {
    opacity: 0 !important;
    visibility: hidden !important;
    pointer-events: none !important;
}

/* GGB 容器 */
.ggb-container {
    width: 100%;
    height: 100%;
    overflow: hidden;
    position: relative;
    touch-action: none;
    overscroll-behavior: contain;
    /* 尺寸完全由 JavaScript 控制。 */
}

body.resources-page .resource-ggb-paused {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 10px;
    padding: 24px;
    box-sizing: border-box;
    color: #475569;
    text-align: center;
    background: #f8fafc;
    touch-action: auto;
}

body.resources-page .resource-ggb-paused>i {
    color: #10b981;
    font-size: 30px;
}

body.resources-page .resource-ggb-paused strong {
    color: #1e293b;
    font-size: 16px;
}

body.resources-page .resource-ggb-paused span {
    font-size: 13px;
}

body.resources-page .resource-ggb-paused button {
    margin-top: 6px;
    padding: 9px 16px;
    border: 0;
    border-radius: 8px;
    color: #fff;
    background: #4a6fa5;
    cursor: pointer;
}

.ggb-container article,
.ggb-container canvas,
.ggb-container .applet_scaler,
.ggb-container .ggbTransform {
    touch-action: none;
    overscroll-behavior: contain;
}

html.ggb-css-fullscreen-lock,
body.ggb-css-fullscreen-lock {
    overflow: hidden !important;
    overscroll-behavior: none;
}

body.ggb-css-fullscreen-lock {
    touch-action: none;
}

/* 隐藏 GeoGebra 自带的加载进度条 */
#ggb-container article>div:first-child,
.ggb-container article>div:first-child {
    display: none !important;
}

.ggb-tips {
    padding: 0.5rem 1.5rem;
    background: var(--primary-bg);
    color: var(--primary-dark);
    font-size: 0.8rem;
    border-top: 1px solid var(--border-color);
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: 0.35rem;
    line-height: 1.45;
}

.ggb-tip-spacer {
    display: inline-block;
    width: 2rem;
    flex: 0 0 2rem;
}

/* 全屏模式 - GGB 展示窗口全屏 */
.ggb-panel.fullscreen {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 9999;
    border-radius: 0;
    margin: 0;
    background: #1a1a2e;
}

.ggb-panel.fullscreen .ggb-header {
    padding: 0.5rem 1rem;
    background: linear-gradient(135deg, var(--subject-color, var(--primary-color)) 0%, var(--subject-dark, var(--primary-dark)) 100%);
    opacity: 0.95;
}

.ggb-panel.fullscreen .ggb-display-area {
    background: #1a1a2e;
}

.ggb-panel.fullscreen .ggb-display-window {
    border-radius: 0;
    box-shadow: 0 0 30px rgba(0, 0, 0, 0.5);
}

.ggb-panel.fullscreen .ggb-tips {
    display: none;
}

/* ========== 旋转全屏模式 - 手机横屏浏览 ========== */
.ggb-panel.rotate-fullscreen {
    position: fixed;
    /* 旋转后：屏幕高度作为宽度，屏幕宽度作为高度。 */
    width: 100vh;
    width: 100dvh;
    height: 100vw;
    height: 100dvw;
    transform: rotate(90deg);
    transform-origin: top left;
    top: 0;
    left: 100vw;
    left: 100dvw;
    z-index: 10000;
    border-radius: 0;
    margin: 0;
    background: #1a1a2e;
}

.ggb-panel.rotate-fullscreen .ggb-header {
    padding: 0.4rem 1rem;
    background: linear-gradient(135deg, var(--subject-color, var(--primary-color)) 0%, var(--subject-dark, var(--primary-dark)) 100%);
    opacity: 0.95;
    flex-wrap: nowrap;
}

/* 横屏模式下重置手机端按钮行，防止按钮竖排错位。 */
.ggb-panel.rotate-fullscreen .ggb-header-right {
    width: auto;
    flex-wrap: nowrap;
    gap: 0.3rem;
    justify-content: flex-end;
}

.ggb-panel.rotate-fullscreen .ggb-header-right button {
    min-width: 44px;
    height: 44px;
    padding: 0 0.65rem;
    font-size: 0.8rem;
}

.ggb-panel.rotate-fullscreen .ggb-header-left h3 {
    font-size: 0.9rem;
}

.ggb-panel.rotate-fullscreen .ggb-path {
    display: none;
}

.ggb-panel.rotate-fullscreen .ggb-display-area {
    background: #1a1a2e;
}

.ggb-panel.rotate-fullscreen .ggb-display-window {
    border-radius: 0;
    box-shadow: 0 0 30px rgba(0, 0, 0, 0.5);
}

.ggb-panel.rotate-fullscreen .ggb-tips {
    display: none;
}

/* 旋转全屏时隐藏原有全屏和购买按钮，但保留刷新按钮。 */
.ggb-panel.rotate-fullscreen .fullscreen-btn,
.ggb-panel.rotate-fullscreen .buy-member-btn {
    display: none !important;
}

.ggb-panel.rotate-fullscreen #refresh-ggb-btn,
.ggb-panel.fullscreen #refresh-ggb-btn {
    display: flex !important;
}

/* 旋转全屏退出按钮 */
.rotate-exit-btn {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.4rem 0.85rem;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 8px;
    color: white;
    font-size: 0.8rem;
    cursor: pointer;
    transition: background 0.2s ease;
    white-space: nowrap;
}

.rotate-exit-btn:hover,
.rotate-exit-btn:active {
    background: rgba(255, 255, 255, 0.35);
}

/* 旋转全屏按钮仅在手机端显示，样式与全屏按钮统一。 */
.rotate-fullscreen-btn {
    display: none;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: var(--radius-md);
    color: white;
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
}

.rotate-fullscreen-btn:hover,
.rotate-fullscreen-btn:active {
    background: rgba(255, 255, 255, 0.35);
}

/* 手机端显示旋转全屏按钮，并保证触控尺寸。 */
@media (max-width: 768px) {
    .rotate-fullscreen-btn {
        display: flex;
        align-items: center;
        justify-content: center;
        min-width: 44px;
        height: 44px;
        padding: 0 0.8rem;
        font-size: 0.8rem;
    }

    .grade-header,
    .ggb-item,
    body.resources-page .resource-ggb-paused button {
        min-height: 44px;
    }

}

/* 加载状态 */
.loading {
    color: var(--text-secondary);
    text-align: center;
    padding: 2rem;
}

/* 错误消息 */
.error-message {
    color: #dc2626;
    background: #fef2f2;
    border: 1px solid #fecaca;
    padding: 1.5rem;
    border-radius: var(--radius-md);
    text-align: center;
}

/* 空状态 */
.empty-state {
    color: #475569;
    font-size: 0.8rem;
    padding: 0.3rem 0.5rem;
    font-style: italic;
}

/* 深层级目录样式 */
.chapter-item[data-level="0"]>.chapter-header {
    font-weight: 500;
    color: #000000;
}

.chapter-item[data-level="1"]>.chapter-header {
    font-size: 0.82rem;
    color: #000000;
}

.chapter-item[data-level="2"]>.chapter-header {
    font-size: 0.8rem;
    padding: 0.35rem 0.4rem;
    min-height: 26px;
    color: #000000;
}

.chapter-item[data-level="3"]>.chapter-header,
.chapter-item[data-level="4"]>.chapter-header,
.chapter-item[data-level="5"]>.chapter-header {
    font-size: 0.78rem;
    padding: 0.3rem 0.35rem;
    min-height: 24px;
    color: #000000;
}

/* 确保所有章节标题都可点击 */
.chapter-header {
    user-select: none;
    -webkit-user-select: none;
    -webkit-tap-highlight-color: transparent;
    cursor: pointer;
}

/* 点击区域扩展 */
.chapter-header::before {
    content: '';
    position: absolute;
    top: -2px;
    left: -4px;
    right: -4px;
    bottom: -2px;
    z-index: -1;
}

/* 空目录仍可点击展开 */
.chapter-header.empty {
    color: #475569;
    cursor: pointer;
}

.chapter-header.empty:hover {
    background: rgba(0, 0, 0, 0.02);
}

/* 深层级章节图标适当缩小 */
.chapter-item[data-level="3"] .chapter-icon,
.chapter-item[data-level="4"] .chapter-icon,
.chapter-item[data-level="5"] .chapter-icon {
    font-size: 0.7rem;
}

/* 响应式课件页面 */
@media (max-width: 1024px) {
    .sidebar {
        width: 280px;
        min-width: 280px;
    }

    /* 较窄侧边栏隐藏模式文字，只显示图标。 */
    .view-mode-section {
        gap: 6px;
        padding: 8px 10px;
    }

    .mode-btn {
        padding: 6px 8px;
    }

    .mode-btn span {
        display: none;
    }
}

@media (max-width: 768px) {
    .chapter-item.folder-item[data-level]>.chapter-header.folder-clickable,
    .chapter-item[data-level]>.chapter-header {
        min-height: 44px;
    }
}

.grade-header:focus-visible,
.chapter-header:focus-visible,
.ggb-item:focus-visible {
    outline: 3px solid #2563eb;
    outline-offset: -2px;
}

.fullscreen-btn:focus-visible,
.rotate-fullscreen-btn:focus-visible,
.rotate-exit-btn:focus-visible,
body.resources-page .resource-ggb-paused button:focus-visible {
    outline: 3px solid #facc15;
    outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
    .grade-header.resource-route-attention {
        animation: none;
        box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.2),
            0 8px 20px rgba(37, 99, 235, 0.18);
    }

    .grade-header,
    .chapter-header,
    .ggb-item,
    .grade-toggle,
    .chapter-toggle,
    .fullscreen-btn,
    .rotate-fullscreen-btn,
    .rotate-exit-btn {
        transition: none;
    }
}