/* 设计令牌 */
:root {
  --color-space-gray: #2d3436;
  --color-matte-black: #000000;
  --color-cement-gray: #b2bec3;
  --color-metallic-accent: #dfe6e9;
  --color-text-primary: #2d3436;
  --color-text-secondary: #636e72;
  --color-background: #ffffff;
  --font-weight-light: 300;
  --letter-spacing-wider: 0.1em;
  --transition-duration: 0.3s;
}

/* 全局样式 */
* {
  box-sizing: border-box;
}

body {
  font-family: "Source Han Sans CN", "Noto Sans SC", sans-serif;
  background-color: var(--color-background);
  color: var(--color-text-primary);
  margin: 0;
  padding: 0;
  line-height: 1.6;
}

/* 导航栏 */
header nav {
  background-color: var(--color-matte-black);
  padding: 1rem 2rem;
  position: fixed;
  width: 100%;
  top: 0;
  z-index: 1000;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

header nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  align-items: center;
  gap: 2rem;
}

header nav a {
  color: var(--color-metallic-accent);
  text-decoration: none;
  font-weight: var(--font-weight-light);
  letter-spacing: 0.05em;
  transition: opacity var(--transition-duration);
}

header nav a:hover {
  opacity: 0.8;
}

/* 页面主内容区 */
main {
  margin-top: 60px;
}

/* 页脚 */
footer {
  text-align: center;
  padding: 1rem;
  font-size: 12pt;
  color: #666;
}

/* 响应式导航菜单 */
@media (max-width: 768px) {
  header nav ul {
    flex-direction: column;
    gap: 1rem;
  }

  header nav {
    flex-direction: column;
  }
}