* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Roboto', Arial, sans-serif;
}

:root {
    --main-color: #2563eb;
    --dark-bg: #1f2937;
    --light-bg: #f3f4f6;
    --text-color: #333;
    --gray-text: #6b7280;
    --border-color: #e5e7eb;
    --white: #ffffff;
}

body {
    background-color: var(--light-bg);
    color: var(--text-color);
    line-height: 1.6;
}

/* 顶部导航 */
.main-header {
    background: var(--white);
    box-shadow: 0 1px 4px rgba(0,0,0,0.08);
    position: sticky;
    top: 0;
    z-index: 999;
}
.header-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.logo {
    font-size: 24px;
    font-weight: 700;
    color: var(--main-color);
    text-decoration: none;
}
.nav-menu a {
    margin-left: 25px;
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: 0.2s;
}
.nav-menu a:hover {
    color: var(--main-color);
}

/* 顶部分类导航 */
.category-nav {
    background: var(--dark-bg);
    padding: 12px 0;
}
.category-wrap {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    gap: 20px;
}
.category-wrap a {
    color: #fff;
    text-decoration: none;
    font-size: 15px;
    opacity: 0.85;
}
.category-wrap a.active {
    opacity: 1;
    font-weight: 500;
}

/* 首页Banner */
.hero-banner {
    background: linear-gradient(135deg,#2563eb,#3b82f6);
    padding: 60px 20px;
    text-align: center;
    color: #fff;
}
.hero-banner h1 {
    font-size: 42px;
    margin-bottom: 15px;
}
.hero-banner p {
    font-size: 18px;
    max-width: 700px;
    margin: 0 auto 30px;
    opacity: 0.9;
}
.btn-primary {
    display: inline-block;
    padding: 14px 35px;
    background: #fff;
    color: var(--main-color);
    font-weight: 600;
    border-radius: 8px;
    text-decoration: none;
    font-size: 16px;
}

/* 主体布局 内容+侧边栏 */
.main-wrap {
    max-width: 1280px;
    margin: 50px auto;
    padding: 0 20px;
    display: grid;
    grid-template-columns: 820px 300px;
    gap: 30px;
}
.main-content {
    background: var(--white);
    padding: 35px;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
.sidebar {
    display: flex;
    flex-direction: column;
    gap: 25px;
}
.side-widget {
    background: var(--white);
    padding: 25px;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
.side-widget h3 {
    font-size: 18px;
    margin-bottom: 18px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}
.side-list a {
    display: block;
    padding: 8px 0;
    color: var(--text-color);
    text-decoration: none;
    font-size: 15px;
}
.side-list a:hover {
    color: var(--main-color);
}

/* 上传转换区域 */
.upload-area {
    border: 2px dashed var(--border-color);
    border-radius: 10px;
    padding: 50px 20px;
    text-align: center;
    margin: 30px 0;
    cursor: pointer;
    transition: all 0.3s ease;
}
.upload-area:hover {
    border-color: var(--main-color);
}
.select-format {
    margin: 25px 0;
    text-align: center;
}
.select-format select {
    padding: 12px 20px;
    font-size: 16px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    min-width: 220px;
}
.convert-btn {
    padding: 13px 40px;
    background: var(--main-color);
    color: #fff;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    cursor: pointer;
    transition: 0.2s;
}
.convert-btn:hover{
    opacity:0.9;
}

/* 广告位 */
.ad-box {
    min-height: 120px;
    background: #f9fafb;
    border: 1px dashed #ccc;
    text-align: center;
    line-height: 120px;
    color: #999;
    margin: 30px 0;
}

/* 文件列表样式 */
.file-list {
    margin: 20px 0;
    padding: 15px;
    background: #f9fafb;
    border-radius: 8px;
    display: none;
}
.file-item {
    padding: 8px 0;
    border-bottom: 1px solid #eee;
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.file-item:last-child {
    border-bottom: none;
}
.file-name {
    font-size: 14px;
    color: var(--text-color);
}
.clear-btn {
    background: #ef4444;
    color: white;
    border: none;
    padding: 4px 10px;
    border-radius: 4px;
    font-size: 12px;
    cursor: pointer;
}
.download-area {
    margin-top: 30px;
    display: none;
}
.download-btn {
    background: var(--main-color);
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 6px;
    text-decoration: none;
    display: inline-block;
    margin: 5px;
    font-size: 14px;
}

/* 底部 */
.main-footer {
    background: var(--dark-bg);
    color: #ccc;
    padding: 50px 20px;
    margin-top: 60px;
}
.footer-container {
    max-width: 1280px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(3,1fr);
    gap: 30px;
}
.footer-col h4 {
    color: #fff;
    margin-bottom: 20px;
    font-size: 17px;
}
.footer-col a {
    display: block;
    color: #ccc;
    text-decoration: none;
    margin: 8px 0;
    font-size: 14px;
}
.copyright {
    text-align: center;
    padding-top: 40px;
    margin-top: 40px;
    border-top: 1px solid #374151;
    font-size: 14px;
}

/* 移动端适配 */
@media (max-width: 1100px) {
    .main-wrap {
        grid-template-columns: 1fr;
    }
}
@media (max-width: 768px) {
    .header-container {
        flex-direction: column;
        gap: 15px;
    }
    .hero-banner h1 {
        font-size: 30px;
    }
    .footer-container {
        grid-template-columns: 1fr;
    }
}