* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: #ffffff;
  color: #1a1a1a;
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* ========== 深色模式 ========== */
html.dark-mode body,
body.dark-mode {
  background: #1a1a1a;
  color: #e0e0e0;
}

html.dark-mode header,
body.dark-mode header {
  border-bottom-color: #333;
}

html.dark-mode header h1,
body.dark-mode header h1 {
  color: #e0e0e0;
}

html.dark-mode .subtitle,
html.dark-mode .intro p,
html.dark-mode .nav-btn p,
body.dark-mode .subtitle,
body.dark-mode .intro p,
body.dark-mode .nav-btn p {
  color: #999;
}

html.dark-mode .nav-btn,
body.dark-mode .nav-btn {
  color: #e0e0e0;
  border-color: #333;
}

html.dark-mode .nav-btn:hover,
body.dark-mode .nav-btn:hover {
  border-color: #666;
  background: #222;
}

.container {
  max-width: 800px;
  width: 100%;
}

header {
  text-align: center;
  margin-bottom: 60px;
  padding-bottom: 30px;
  border-bottom: 1px solid #e0e0e0;
}

header h1 {
  font-size: 3rem;
  font-weight: 700;
  color: #1a1a1a;
  margin-bottom: 10px;
  letter-spacing: 2px;
}

.subtitle {
  font-size: 1rem;
  color: #666;
  font-weight: 400;
  letter-spacing: 1px;
}

.intro {
  margin-bottom: 50px;
  text-align: center;
}

.intro p {
  font-size: 1.1rem;
  color: #333;
  line-height: 1.8;
}

.nav-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 30px;
  margin-bottom: 40px;
}

.nav-btn {
  display: block;
  padding: 40px 30px;
  text-decoration: none;
  color: #1a1a1a;
  border: 1px solid #e0e0e0;
  transition: all 0.2s ease;
  text-align: center;
}

.nav-btn:hover {
  border-color: #1a1a1a;
  background: #fafafa;
}

.nav-btn h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 8px;
  letter-spacing: 1px;
}

.nav-btn p {
  font-size: 0.9rem;
  color: #666;
  font-weight: 400;
}

/* ========== 響應式設計 ========== */
@media (max-width: 768px) {
  header h1 {
    font-size: 2rem;
  }

  .intro p {
    font-size: 1rem;
  }

  .nav-links {
    grid-template-columns: 1fr;
  }

  .nav-btn {
    padding: 30px 20px;
  }
}

/* ========== 主題切換按鈕 ========== */
.theme-toggle {
  position: fixed;
  top: 20px;
  right: 20px;
  background: none;
  border: 1px solid #e0e0e0;
  padding: 10px 15px;
  cursor: pointer;
  font-size: 1.2rem;
  transition: all 0.2s ease;
  z-index: 1000;
}

.theme-toggle:hover {
  border-color: #1a1a1a;
  background: #fafafa;
}

html.dark-mode .theme-toggle,
body.dark-mode .theme-toggle {
  border-color: #333;
}

html.dark-mode .theme-toggle:hover,
body.dark-mode .theme-toggle:hover {
  border-color: #666;
  background: #222;
}