body {
  font-family: 'Segoe UI', Arial, sans-serif;
  margin: 0;
  background: linear-gradient(135deg, #f7f9fc 60%, #e3eaf7 100%);
  color: #222;
}
header {
  background: linear-gradient(90deg, #0057b7 80%, #0077ff 100%);
  color: #fff;
  padding: 1.5rem 0 1rem 0;
  box-shadow: 0 2px 8px rgba(0,87,183,0.08);
}
header h1 {
  margin: 0;
  font-size: 2.4rem;
  text-align: center;
  letter-spacing: 1px;
  font-weight: 700;
}
nav ul {
  display: flex;
  justify-content: center;
  align-items: center;
  list-style: none;
  padding: 0;
  margin: 1rem 0 0 0;
  flex-wrap: wrap;
}
nav li {
  margin: 0 1rem;
  position: relative;
}
nav a {
  color: #fff;
  text-decoration: none;
  font-weight: 500;
  padding: 0.4rem 1rem;
  border-radius: 6px;
  transition: background 0.2s, color 0.2s;
}
nav a:hover, nav a:focus {
  background: rgba(255,255,255,0.18);
  color: #ffe600;
}
nav select {
  padding: 0.35rem 0.7rem;
  border-radius: 6px;
  border: none;
  font-size: 1em;
  background: #fff;
  color: #0057b7;
  box-shadow: 0 1px 4px rgba(0,87,183,0.08);
  cursor: pointer;
}
main {
  max-width: 700px;
  margin: 2.5rem auto;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 4px 24px rgba(0,87,183,0.10);
  padding: 2rem 2.2rem;
  min-height: 350px;
}
section {
  margin-bottom: 2.5rem;
}
h2 {
  color: #0057b7;
  margin-top: 0;
  font-size: 1.5rem;
  font-weight: 600;
  letter-spacing: 0.5px;
}
footer {
  text-align: center;
  padding: 1.2rem 0 0.7rem 0;
  background: #f2f5fa;
  color: #555;
  border-top: 1px solid #dbe3ef;
  font-size: 1em;
  box-shadow: 0 -2px 8px rgba(0,87,183,0.04);
}

/* 按钮样式（如有需要可用于表单） */
.btn {
  display: inline-block;
  background: #0057b7;
  color: #fff;
  border: none;
  border-radius: 6px;
  padding: 0.5rem 1.2rem;
  font-size: 1em;
  font-weight: 500;
  cursor: pointer;
  box-shadow: 0 2px 8px rgba(0,87,183,0.08);
  transition: background 0.2s;
}
.btn:hover, .btn:focus {
  background: #0077ff;
}

/* 响应式优化 */
@media (max-width: 800px) {
  main {
    padding: 1.2rem 0.7rem;
    max-width: 98vw;
  }
  header h1 {
    font-size: 1.5rem;
  }
}
@media (max-width: 600px) {
  main {
    padding: 1rem 0.3rem;
    margin: 1rem auto;
  }
  nav ul {
    flex-direction: column;
    align-items: stretch;
  }
  nav li {
    margin: 0.5rem 0;
  }
  header h1 {
    font-size: 1.1rem;
  }
}