.main_top {
  width: 100%;
}
.main_nav_top {
  width: 80%;
  margin: 20px auto;
  display: flex;
}
.main_nav_item {
  width: 100%;
}
.main_nav_item .main_nav_item_a {
  color: #ccc;
  margin: 0 20px;
  padding: 10px 0;
  border-bottom: 2px solid #fff;
}
.main_nav_item .main_nav_item_select {
  color: rgb(75, 137, 218);
  border-bottom: 2px solid rgb(75, 137, 218);
}
.main_nav {
  width: 100%;
  text-align: right;
}
.main_nav a {
  color: #ccc;
}
.main_nav span {
  color: #ccc;
  display: inline-block;
  margin: 0 5px;
}
.introduce {
  padding: 5% 5% 0% 5%;
  position: relative;
}
.main_item {
  width: 70%;
  margin: 0 auto;
}
.main_item_title {
  text-align: center;
  font-size: 25px;
  font-weight: 700;
}
.main_item_content {
  font-size: 20px;
  line-height: 40px;
}
#main_item02 {
  display: none;
  padding-bottom: 50px;
}
.aboutus {
  height: 574px;
}
.activity {
  border: 0px;
  border-bottom: 1px solid #000;
  margin: 30px;
  font-size: 20px;
  padding: 10px;
  width: 300px;
  /* appearance: none; */
  /*-moz-appearance: none; /* Firefox */
  /* -webkit-appearance: none; /* Safari 和 Chrome */
}
.post_list {
  padding: 0 30px;
  margin: 0 auto 40px;
}
.post_list .post_item p {
  font-size: 20px;
  font-weight: 700;
}
.post_list .post_item span {
  display: block;
  line-height: 40px;
}