.books-nav-wrap {
  padding: 45px 5%;
}

.books-nav-wrap .nav li {
  display: block;
  width: 152px;
  height: 45px;
  line-height: 45px;
  text-align: center;
  float: left;
  margin-right: 19px;
  margin-bottom: 20px;
  user-select: none;
}

.books-nav-wrap .nav li a {
  color: #fff;
}

.books-nav-wrap .nav li:nth-of-type(5n+1) {
  background-color: #057dba;
}

.books-nav-wrap .nav li:nth-of-type(5n+2) {
  background-color: #6f05ba;
}

.books-nav-wrap .nav li:nth-of-type(5n+3) {
  background-color: #ba055a;
}

.books-nav-wrap .nav li:nth-of-type(5n+4) {
  background-color: #ba8905;
}

.books-nav-wrap .nav li:nth-of-type(5n) {
  background-color: #63ba05;
}

.books-nav-wrap .nav li:nth-of-type(5n) {
  background-color: #63ba05;
}

.books-nav-wrap .books-intro {
  margin-top: 22px;
}

.books-intro .left {
  float: left;
  width: 50%;
}

.books-intro .left img {
  width: 100%;
}

.books-intro .right {
  float: right;
  width: 50%;
  padding: 20px 0 20px 20px;
}

.books-intro .right h3 {
  font-size: 38px;
  padding: 0 10px 10px 10px;
  border-bottom: 1px solid #cccccc;
}

.books-intro .right .content {
  padding: 10px;
  border-bottom: 1px solid #cccccc;
}

.books-intro .right .electronic-btn {
  padding: 10px;
}

.books-intro .right .electronic-btn a {
  width: 150px;
  height: 48px;
  border: solid 1px #bfbfbf;
  font-size: 16px;
  color: #333;
  display: block;
  text-align: center;
  line-height: 48px;
}

.books-intro .right .electronic-btn a:hover {
  color: #fff;
  background-color: #057dba;
  border-color: #057dba;
}

.books-picture-list {
  background-color: #000;
  padding: 0 5%;
}

.books-picture-list .content {
  background-color: #333333;
  padding: 20px 30px;
}

.books-picture-list .item {
  text-align: center;
  cursor: pointer;
}

.books-picture-list img {
  width: 100%;
  height: auto;
}

.books-picture-list .img {
  position: relative;
}

.books-picture-list .img .thum {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(5, 125, 186, 0.8);
  transition: transform 0.5s, opacity 0.5s;
  opacity: 0;
  visibility: hidden;
  transform: scale(0);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 32px;
}

.books-picture-list .item:hover .thum {
  visibility: visible;
  opacity: 1;
  transform: scale(1);
}

.books-picture-list h4 {
  font-size: 18px;
  color: #fff;
  margin-top: 15px;
}

.books-picture-list p {
  font-size: 14px;
  color: #ccc;
}

@media (max-width: 1200px) {
  .books-intro .left {
    float: none;
    width: 100%;
  }

  .books-intro .right {
    float: none;
    width: 100%;
    padding-left: 0;
  }
}

@media (max-width: 768px) {
  .books-intro .right h3 {
    font-size: 24px;
  }
}