:root {
  --text-base: 15px;
  --text-large: 1.5rem;
  --line-height: 1.5;
  --bg-color: #fafafa;
  --text-color: #222;
  --header-bg: #0070f3;
  --header-text: white;
  --main-bg: white;
  --main-shadow: rgba(0, 0, 0, 0.05);
  --link-color: #0070f3;
  --footer-color: #666;
  --lang-menu-bg: white;
  --lang-menu-text: #222;
  --lang-menu-hover: #f5f5f5;
  --lang-menu-shadow: rgba(0, 0, 0, 0.15);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-color: #1a1a1a;
    --text-color: #e4e4e4;
    --header-bg: #0052b3;
    --header-text: #e4e4e4;
    --main-bg: #2a2a2a;
    --main-shadow: rgba(0, 0, 0, 0.3);
    --link-color: #4a9eff;
    --footer-color: #a0a0a0;
    --lang-menu-bg: #2a2a2a;
    --lang-menu-text: #e4e4e4;
    --lang-menu-hover: #3a3a3a;
    --lang-menu-shadow: rgba(0, 0, 0, 0.5);
  }
}

@media (min-width: 1024px) {
  :root {
    --text-base: 14.5px;
    --line-height: 1.55;
  }
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", "Segoe UI",
    Roboto, "PingFang SC", "Hiragino Sans GB", "Noto Sans CJK SC",
    "Microsoft YaHei", sans-serif;
  font-size: var(--text-base);
  line-height: var(--line-height);
  background-color: var(--bg-color);
  color: var(--text-color);
  margin: 0;
  padding: 0;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

header {
  background-color: var(--header-bg);
  color: var(--header-text);
  padding: 1.8rem 1rem;
  text-align: center;
  position: relative;
}

header h1 {
  font-size: var(--text-large);
  margin-bottom: 0.3rem;
}

header p {
  margin: 0.2rem 0 0;
  font-size: 0.95rem;
  opacity: 0.9;
}

main {
  max-width: 800px;
  margin: 2rem auto;
  padding: 1.8rem 1.5rem;
  background: var(--main-bg);
  border-radius: 12px;
  box-shadow: 0 2px 8px var(--main-shadow);
}

h2 {
  color: var(--link-color);
  font-size: 1.15rem;
  margin-top: 1.6rem;
  margin-bottom: 0.6rem;
}

p {
  margin: 0.4rem 0 0.8rem;
  font-size: 0.97rem;
}

ul {
  margin: 0.4rem 0 1rem 1.2rem;
  padding: 0;
}
ul li {
  margin-bottom: 0.3rem;
  font-size: 0.95rem;
}

a {
  color: var(--link-color);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

footer {
  text-align: center;
  font-size: 0.9rem;
  color: var(--footer-color);
  margin: 2rem 0 3rem;
}

.lang-switch-container {
  position: absolute;
  right: 1rem;
  top: 1rem;
}

.lang-switch {
  background: rgba(255, 255, 255, 0.2);
  color: white;
  border: none;
  padding: 0.35rem 0.75rem;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.85rem;
  transition: background 0.2s ease;
}
.lang-switch:hover {
  background: rgba(255, 255, 255, 0.35);
}

.lang-menu {
  display: none;
  position: absolute;
  right: 0;
  top: 100%;
  margin-top: 0.5rem;
  background: var(--lang-menu-bg);
  border-radius: 6px;
  box-shadow: 0 4px 12px var(--lang-menu-shadow);
  min-width: 120px;
  overflow: hidden;
  z-index: 1000;
}

.lang-option {
  display: block;
  width: 100%;
  padding: 0.6rem 1rem;
  border: none;
  background: var(--lang-menu-bg);
  color: var(--lang-menu-text);
  text-align: left;
  cursor: pointer;
  font-size: 0.85rem;
  transition: background 0.2s ease;
}

.lang-option:hover {
  background: var(--lang-menu-hover);
}

@media (max-width: 600px) {
  header {
    padding: 1.5rem 1rem;
  }
  main {
    margin: 1rem;
    padding: 1.2rem 1rem;
  }
  h1 {
    font-size: 1.3rem;
  }
  h2 {
    font-size: 1.05rem;
  }
}