/* 主导航 */
.main-nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  display: flex;
  background-color: #2c3e50;
  height: 50px;
  justify-content: center;
  border-bottom: 2px solid #3498db;
}

.main-nav li {
  margin: 0 3px;
  display: flex;
  align-items: center;
}

.main-nav li a {
  display: block;
  color: #FFFFFF;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-family: 'Segoe UI', sans-serif;
  font-size: 14px;
  font-weight: 500;
  transition: all 0.3s ease;
}

.main-nav li a:hover {
  background-color: #3498db;
  color: white;
}

.main-nav li a.active {
  position: relative;
  color: white !important;
}

.main-nav li a.active::after {
  content: "";
  display: block;
  position: absolute;
  bottom: -8px;
  left: 50%;
  transform: translateX(-50%);
  width: 110%;
  height: 3px;
  background-color: #3498db;
  border-radius: 2px;
}