/* ===== 基础重置 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* ===== 布局：页脚贴底 + 宽屏内容 ===== */
html {
    height: 100%;
}

body {
    min-height: 100%;
    display: flex;
    flex-direction: column;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

/* 主内容区：撑开以推动页脚到底部 */
.main-content {
    flex: 1;
    width: 100%;
    padding: 2rem 0; /* 上下留白 */
}

/* 讲义区域：宽屏风格，与主站视觉一致 */
.lectures-section {
    max-width: 1400px; /* 主站常用宽度范围 */
    width: 92%;        /* 大屏占 92%，小屏自适应 */
    margin: 0 auto;    /* 水平居中 */
    background-color: #ffffff;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    padding: 1.8rem;
}

/* ===== 列表样式 ===== */
.lectures-list {
    list-style: none;
}

.lectures-item {
    padding: 1rem 0;
    border-bottom: 1px solid #eee;
}

.lectures-item:last-child {
    border-bottom: none;
}

.lectures-link {
    text-decoration: none;
    color: #2980b9;
    font-weight: 600;
    font-size: 1.5rem;
    display: block;
    transition: color 0.2s ease;
}

.lectures-link:hover {
    color: #e74c3c;
    text-decoration: underline;
}

.update-notes {
    list-style-type: disc;
    margin-top: 0.6rem;
    margin-left: 1.3rem;
    padding-left: 0;
    color: #7f8c8d;
    font-size: 0.98rem;
}

.update-notes li {
    margin-top: 0.35rem;
}

/* ===== 导航栏 ===== */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2.5rem;
    background-color: #ffffff;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.08);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-img {
    height: 40px;
    width: auto;
}

.logo-text {
    font-size: 24px;
    font-weight: bold;
    background: linear-gradient(45deg, #3498db, #2ecc71);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    color: transparent;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 1.6rem;
}

.nav-links a {
    text-decoration: none;
    color: #34495e;
    font-weight: 500;
    font-size: 1.05rem;
    transition: color 0.3s ease;
}

.nav-links a:hover {
    color: #3498db;
}

/* ===== 页脚 ===== */
.footer {
    text-align: center;
    padding: 2.2rem 1rem;
    color: #7f8c8d;
    font-size: 0.92rem;
    border-top: 1px solid #eee;
    background-color: #ffffff;
}