/* 只给内容区域加灰色背景，导航保持白色不变 */
.course-wrapper {
    background-color: #f7f8fa;
    padding: 40px 0;
}

/* 全局容器 */
.course-container {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    gap: 24px;
    padding: 0 20px;
    align-items: flex-start;
}

/* ===================== 左侧导航 ===================== */
.course-nav-left {
    width: 260px;
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.05);
    padding: 24px;
    position: sticky;
    top: 40px;
}

.course-nav-left h3 {
    font-size: 16px;
    color: #111;
    margin-bottom: 16px;
    padding-bottom: 10px;
    border-bottom: 1px solid #eee;
}

.course-nav-left ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.course-nav-left li {
    padding: 10px 12px;
    font-size: 14px;
    color: #555;
    border-radius: 6px;
    cursor: pointer;
    margin-bottom: 4px;
    transition: 0.2s;
}

.course-nav-left li.course-active,
.course-nav-left li:hover {
    background-color: #f0f7ff;
    color: #2d8cf0;
}

/* ===================== 中间内容 ===================== */
.course-content-main {
    flex: 1;
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.05);
    padding: 48px;
}

.course-content-main h1 {
    font-size: 30px;
    color: #222;
    margin-bottom: 24px;
    font-weight: 600;
}

.course-content-main h2 {
    font-size: 22px;
    margin: 36px 0 16px;
    color: #222;
    padding-bottom: 8px;
    border-bottom: 1px solid #eee;
}

.course-content-main h3 {
    font-size: 18px;
    margin: 24px 0 12px;
}

.course-content-main p {
    font-size: 15px;
    color: #444;
    margin-bottom: 16px;
}

.course-content-main ul {
    margin: 0 0 16px 22px;
}

.course-content-main li {
    margin-bottom: 8px;
    color: #444;
}

/* 代码块 */
.course-code-block {
    background: #f7f8fa;
    border-left: 3px solid #2d8cf0;
    padding: 16px 20px;
    border-radius: 8px;
    margin: 20px 0;
    font-family: Consolas, monospace;
    font-size: 14px;
    color: #333;
    overflow-x: auto;
}

/* ===================== 右侧目录 ===================== */
.course-toc-right {
    width: 240px;
    background: #fff;
    border-radius: 12px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.05);
    padding: 24px;
    position: sticky;
    top: 40px;
}

.course-toc-right h3 {
    font-size: 16px;
    margin-bottom: 16px;
    color: #111;
    padding-bottom: 10px;
    border-bottom: 1px solid #eee;
}

.course-toc-right ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.course-toc-right li {
    padding: 6px 0;
    font-size: 14px;
    color: #666;
    cursor: pointer;
    transition: 0.2s;
}

.course-toc-right li.course-active,
.course-toc-right li:hover {
    color: #2d8cf0;
    padding-left: 4px;
}

/* 适配小屏幕 */
@media (max-width: 1024px) {
    .course-container {
        flex-direction: column;
    }
    .course-nav-left, .course-toc-right {
        width: 100%;
        position: static;
    }
}