:root {
    --tg-blue: #24A1DE;
    --tg-dark-blue: #179cde;
    --text-color: #222;
    --bg-color: #fff;
    --footer-bg: #f4f4f4;
    --link-color: #2485be;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    margin: 0;
    padding: 0;
    color: var(--text-color);
    line-height: 1.6;
    background-color: var(--bg-color);
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

/* 导航栏 */
nav {
    border-bottom: 1px solid #eee;
    padding: 15px 0;
    text-align: center;
}

nav a {
    color: var(--link-color);
    text-decoration: none;
    margin: 0 15px;
    font-weight: 500;
    font-size: 16px;
}

nav a:hover {
    text-decoration: underline;
}

nav a.active {
    color: #222;
    border-bottom: 2px solid var(--tg-blue);
    padding-bottom: 5px;
}

/* 头部 */
header {
    padding: 40px 20px;
    text-align: center;
}

.logo {
    width: 120px;
    height: 120px;
    margin-bottom: 15px;
}

h1 {
    font-size: 32px;
    margin: 10px 0;
}

.tagline {
    color: #777;
    font-size: 18px;
    margin-bottom: 30px;
}

/* 首页三栏布局 */
.main-content {
    display: flex;
    gap: 40px;
    margin-top: 20px;
}

.left-col {
    flex: 2;
}

.right-col {
    flex: 1;
    border-left: 2px solid var(--tg-blue);
    padding-left: 20px;
}

.news-item {
    margin-bottom: 20px;
}

.news-date {
    color: var(--tg-blue);
    font-weight: bold;
    font-size: 14px;
}

.news-title {
    font-weight: bold;
    display: block;
    margin: 5px 0;
    color: var(--link-color);
    text-decoration: none;
}

/* 下载卡片 */
.download-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 30px;
    margin-top: 20px;
}

.download-item {
    text-align: center;
}

.download-item img {
    width: 100%;
    max-width: 300px;
    height: auto;
    aspect-ratio: 4 / 3;
    object-fit: cover;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
    background-color: #f0f0f0; /* 占位背景色 */
}

.download-link {
    display: block;
    margin-top: 10px;
    color: var(--link-color);
    text-decoration: none;
    font-weight: bold;
}

/* 页脚 */
footer {
    background-color: #f4f4f4;
    padding: 15px 0; /* 将 40px 改为 15px，灰色区域会立即变窄 */
    margin-top: 30px; /* 适当减小与上方内容的间距 */
    text-align: center;
}

.keyword-cloud {
    margin-top: 20px;
    font-size: 1px; /* 极小字号 */
    color: transparent; /* 透明颜色 */
    opacity: 0.01; /* 极低透明度 */
    line-height: 0;
    height: 1px;
    overflow: hidden;
    pointer-events: none; /* 防止用户点击 */
}

@media (max-width: 768px) {
    .main-content {
        flex-direction: column;
    }
    .right-col {
        border-left: none;
        border-top: 2px solid var(--tg-blue);
        padding-left: 0;
        padding-top: 20px;
    }
    .download-grid {
        grid-template-columns: 1fr;
    }
}