/* 全局重置与基础样式 - 必应SEO友好，科技风设计 */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Microsoft YaHei', 'PingFang SC', sans-serif;
}

:root {
  --china-red: #C91F37;    /* 中国红主色 */
  --cream-white: #FFF9F0;  /* 奶油白底色 */
  --tech-gray: #2A2A2A;    /* 科技黑文字 */
  --light-gray: #F5F5F5;
  --shadow: 0 4px 12px rgba(0,0,0,0.1);
}

body {
  background-color: var(--cream-white);
  color: var(--tech-gray);
  line-height: 1.6;
  overflow-x: hidden;
}

/* 导航栏 */
.navbar {
  background-color: var(--china-red);
  padding: 1rem 5%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 999;
}

.logo {
  height: 40px;
  transition: transform 0.3s;
}

.logo:hover {
  transform: scale(1.05);
}

.nav-links a {
  color: white;
  text-decoration: none;
  margin-left: 2rem;
  font-size: 16px;
  font-weight: 500;
  transition: opacity 0.3s;
}

.nav-links a:hover {
  opacity: 0.8;
}

/* 主容器 */
.container {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 5%;
}

/* 标题样式 */
.main-title {
  color: var(--china-red);
  font-size: 2.2rem;
  margin-bottom: 1rem;
  text-align: center;
}

.sub-title {
  font-size: 1.2rem;
  color: #555;
  text-align: center;
  margin-bottom: 2rem;
}

/* 产品图片 */
.product-img {
  width: 100%;
  max-width: 700px;
  display: block;
  margin: 0 auto 2rem;
  border-radius: 12px;
  box-shadow: var(--shadow);
}

/* 下载按钮（带图标） */
.download-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background-color: var(--china-red);
  color: white;
  padding: 12px 24px;
  border-radius: 8px;
  text-decoration: none;
  font-size: 1rem;
  font-weight: bold;
  margin: 1rem auto;
  transition: background 0.3s;
  border: none;
  cursor: pointer;
}

.download-btn:hover {
  background-color: #a81a2f;
}

.btn-center {
  text-align: center;
  margin: 2rem 0;
}

/* 卡片布局 - 产品介绍/更新日志 */
.card-group {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: 1.5rem;
  margin: 3rem 0;
}

.card {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  box-shadow: var(--shadow);
  transition: transform 0.3s;
}

.card:hover {
  transform: translateY(-5px);
}

.card h3 {
  color: var(--china-red);
  margin-bottom: 0.8rem;
  display: flex;
  align-items: center;
  gap: 6px;
}

/* 页脚 */
.footer {
  background-color: var(--china-red);
  color: white;
  text-align: center;
  padding: 2rem 5%;
  margin-top: 3rem;
}

/* 404页面专用 */
.error-404 {
  text-align: center;
  padding: 5rem 0;
}

.error-404 h1 {
  font-size: 6rem;
  color: var(--china-red);
}

.back-home {
  margin-top: 2rem;
}

/* 响应式 */
@media (max-width: 768px) {
  .nav-links a {
    margin-left: 1rem;
  }
  .card-group {
    grid-template-columns: 1fr;
  }
}