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

html {
    font-size: 62.5%;
    font-family: 'Roboto', sans-serif;
}

li {
    list-style: none;
}

a {
    text-decoration: none;
}

.header{
    border-bottom: 1px solid #E2E8F0;
    
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
}

.hamburger {
    display: none;
}

.bar {
    display: block;
    width: 25px;
    height: 3px;
    margin: 5px auto;
    -webkit-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
    background-color: #101010;
}

.nav-menu {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-item {
    margin-left: 5rem;
}

.nav-link{
    font-size: 1.6rem;
    font-weight: 400;
    color: #475569;
}

.nav-link:hover,footer a:hover{
    color: #4fc08d;
}

.nav-logo {
    font-size: 2.1rem;
    font-weight: 500;
    color: #304455;
    display: flex;
    flex-direction: row;
    align-items: center;
}

.logo_img{
  width: 4rem;
  height: 4rem;
}

@media only screen and (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 7.3rem;
        flex-direction: column;
        background-color: #fff;
        width: 100%;
        border-radius: 10px;
        text-align: center;
        transition: 0.3s;
        box-shadow:
            0 10px 27px rgba(0, 0, 0, 0.05);
        
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-item {
        margin: 2.5rem 0;
    }

    .hamburger {
        display: block;
        cursor: pointer;
    }

    .hamburger.active .bar:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active .bar:nth-child(1) {
        -webkit-transform: translateY(8px) rotate(45deg);
        transform: translateY(8px) rotate(45deg);
    }

    .hamburger.active .bar:nth-child(3) {
        -webkit-transform: translateY(-8px) rotate(-45deg);
        transform: translateY(-8px) rotate(-45deg);
    }
}

.container{
  width: 90%;
  margin: 4.6rem auto;
  display: flex;
  flex-direction: row;
  justify-content: center;
  flex-wrap: wrap;
  padding: 1rem;
}
.wrap_right{
  flex: 1;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  /* background-color: lightcyan; */
}
.book_title{
  font-size: 28px;
  font-weight: 500;
  line-height: 1.5;
  margin: 0 auto;
}
.book_desc{
  font-size: 15px;
  line-height: 3;
  text-indent: 2em;
  text-align:justify;
  text-justify:inter-ideograph;
}
footer{
   border-top: 1px solid #E2E8F0;
   background-color: white;
   width: 100vw;
   text-align: center;
   padding: 1.5rem 0;
   z-index: 1000;
   position: fixed;
   bottom: 0;
   font-size: 1.2rem;
}
.transback{
  display: none;
  line-height: 40px;
  background-color: #ccc;
  width: 100%;
  height: 100%;
  left:0;
  top:0;/*FF IE7*/
  filter:alpha(opacity=90);/*IE*/
  opacity:0.9;/*FF*/
  z-index:1;
  
  position:fixed!important;/*FF IE7*/
  position:absolute;/*IE6*/
  _top:       expression(eval(document.compatMode &&
              document.compatMode=='CSS1Compat') ?
              documentElement.scrollTop + (document.documentElement.clientHeight-this.offsetHeight)/2 :/*IE6*/
              document.body.scrollTop + (document.body.clientHeight - this.clientHeight)/2);/*IE5 IE5.5*/
}
.popdiv1,.popdiv2 {
     display: none;
     position:fixed;
     margin:auto;
     left:0;
     right:0;
     top:0;
     bottom:0;
     z-index:99;
     line-height: 40px;
     padding:10px;
      /*设置div的宽和高*/
     background-color: #fff;
     border: 1px solid #f90;
     width: 90%;
     height: 70vh;
     text-align: center;
     overflow: scroll;
}
.popdiv1 img{
     height: 100%;
     width: auto;
}
.popdiv2-flex{
  display: flex;
  flex-direction: row;
  justify-content: center;
}
.popdiv2-flex img{
  margin: 0.3rem;
  max-width: 100%;
  height: auto;
  border: 1px solid black;
}