* {                     /*reset the default styles of HTML elements*/
    padding: 0;
    margin: 0;
    text-decoration: none;
    list-style: none;
    box-sizing: border-box;
}

body {
    font-family: Lato,serif;
    background-color: #f2f2f2;
}

  /* styling nav bar */
nav{
    position: fixed;
    top: 0;
    z-index: 2;
    font-family: 'Poppins', sans-serif;
    display: flex;
    height: 95px;
    width: 100%;
    background-color: transparent;
    align-items: center;
    justify-content: space-between;
    padding: 0 0 0 50px;
    flex-wrap: wrap;
    transition: background-color 0.2s ease-in-out;
}

nav.scrolled {
    background-color: #253177;

}  

.logo.scrolled {
    color: #fff;
}

nav ul li a.scrolled  {
    color: #f2f2f2;
}   

nav .tutor.scrolled {
    color: #fff;
    background-color: #374EFF;
    font-weight: 700;
    font-size: 14px;
    padding: 15px 40px;
    border-radius: 4px;
    box-shadow: 3px 3px 7px 2px rgb(109 121 255 / 30%);
}


  nav .logo{
    color: rgb(99, 118, 161);
    transition: color 0.2s ease-in-out;
    font-size: 35px;
    font-weight: 600;   

  }
  nav ul{
    display: flex;
    flex-wrap: wrap;
    list-style: none;
    position: absolute;
    left: 20%;
    top: 30%;
    width: 100%;
  }

  nav ul li{
    margin: 0 10px;
    position: relative;
  }
  
  .search-form input[type="text"] {   /*attribute selector, using attribute to style, attribute = "value" */
    padding: 5px;                   /*为指定的attribute加上css*/
    border-radius: 5px;             /*exp: input[type="text"] targets all <input> elements that have a type attribute with a value of text.*/
    width: 500px;
    height: 33px;
    outline: none;  /* Remove the default blue outline */
    border: none;
}


.search-form {
    border: 0.5px solid lightgray;
    background-color: white;
    border-radius: 7px;
}
  
.search-form button[type="submit"] {
    background-color: transparent;
    color: gray;    
    border: none;
    padding: 5px 10px;
    cursor: pointer;
    transition: background-color 0.3s ease;
}
  nav ul li a{
    color: rgb(99, 118, 161);
    font-size: 18px;
    font-weight: 500;
  }


  nav .menu-btn i{
    color: #fff;   
    font-size: 22px;
    cursor: pointer;
    display: none;
  }
  
  input[type="checkbox"]{
    display: none;
  }

.layer {
    width: 70px;
    height: 70px;
    transition: 0.3s;
    margin-left: 10px;
}

.layer i{
    position: absolute;
    top: 0;
    left: 0;
    width: 40%;
    height: 45%;
    border: 1px solid var(--c);
    border-radius: 6px;
    transition: 0.3s;
    display: flex;
    justify-content: center;
    align-items: center;
}

nav .text { 
    position: absolute;
    bottom: 0;
    opacity: 0;
    width: 100%;
    left: -30%;
    text-align: center;
    color: var(--c);        /* call var() to a customization --c */
    transition: 0.3s;
}

nav ul a:hover .text {
    opacity: 1;
}


nav li a:hover .layer {
    transform: rotate(-35deg) skew(20deg);
}

nav li a:hover .layer i:nth-child(1) {
    opacity: 0.2;
    transform: translate(0,0);
}

nav li a:hover .layer i:nth-child(2) {
    opacity: 0.4;
    transform: translate(5px,-5px);
}

nav li a:hover .layer i:nth-child(3) {
    opacity: 0.6;
    transform: translate(10px,-10px);
}

nav li a:hover .layer i:nth-child(4) {
    opacity: 0.8;
    transform: translate(15px,-15px);
}

nav li a:hover .layer i:nth-child(5) {
    opacity: 1.0;
    transform: translate(20px,-20px);
}

/* customize --c */
nav li:nth-child(1) .layer i, li:nth-child(1) .text {
    --c: #12b7f5;
}

nav li:nth-child(2) .layer i, li:nth-child(2) .text {
    --c: #2aae67;
}


nav li:nth-child(3) .layer i, li:nth-child(3) .text {
    --c: #e79115;
}


nav li:nth-child(4) .layer i, li:nth-child(4) .text {
    --c: #2075fd;
    
}


nav li:nth-child(5) .layer i, li:nth-child(5) .text {
    --c: #2d8dc5;
}

nav li:nth-child(7) .layer i, li:nth-child(7) .text {
    --c: rgb(198, 56, 56);
}

.icon-badge {
    display: inline-block;
    position: relative;
}

.icon-badge .badge {
    display: block;
    position: absolute;
    top: 0;
    bottom: 10px;
    right: 0;
    left: 15px;
    width: 15px;
    height: 15px;
    text-align: center;
    background-color: gray;
    color: #fff;
    font-size: 12px;
    font-weight: bold;
    border-radius: 50%;
}

.payment {
    position: fixed;
    z-index: 3;
    top: 13%;
    left: 95%;
}  

/* styling main body */
.green {
    width: 100%;
    height: 800px;
    position: relative;
}

/* styling subtitlte */
.subt { 
    margin-top: 8em;
    text-align: center;
    line-height: 1.5;
    display: inline-block;  
}

.subt > p {
    background-color: rgb(40, 37, 37);
    color: white;
    width: 89em;
    padding: 10px 0;
}


/* styling reflect images */
.rotate-books {
    position: relative;
    width: 100%;
    height: 500px;
    margin-top: 0;
}

.rotbook {
    position: absolute;
    width: 350px;
    height: 200px;
    left: 38%;
    top: 30%;    
    display: flex;
    transform-style: preserve-3d;
    animation: action 35s linear infinite;
}

.rotbook:hover {
    cursor: pointer;
    animation-play-state: paused;
}

@keyframes action {
    from {
      transform: rotateY(0deg);
    }
    to {
      transform: rotateY(360deg);
    }
}

.rotbook img {
    width: 350px;
    -webkit-box-reflect: below 15px -webkit-linear-gradient(transparent 10%, rgba(255,255,255,0.3));
    height: 200px;
    position: absolute;
}
.rotbook img:nth-child(1) {
    transform: translateZ(500px);
}
.rotbook img:nth-child(2) {
    transform: rotateY(60deg) translateZ(500px);
}
.rotbook img:nth-child(3) {
    transform: rotateY(120deg) translateZ(500px);
}
.rotbook img:nth-child(4) {
    transform: rotateY(180deg) translateZ(500px);
}
.rotbook img:nth-child(5) {
    transform: rotateY(240deg) translateZ(500px);
}
.rotbook img:nth-child(6) {
    transform: rotateY(300deg) translateZ(500px);
}

.p-a h1 {
    margin-top: 30px;
    font-family: Poynter,Georgia,serif;
    font-weight: 400;
    font-size: 2.5rem;
}

.p-a {
    position: absolute;
    bottom: 0;
    text-align: center;
    left: 30%;
}

/* styling all books */
.container {
    width: 100%;
    position: relative;
    height: 3300px;
}

.button-grp {
    position: absolute;
    left: 70px;
    font-family: Lato, sans-serif;
    font-size: 14px;
    font-style: normal;
    font-weight: 400;
    line-height: 35px;
}

.button-grp a {
    display: flex;
}

.button-grp h2 {
    margin-top: 30px;
    font-size: 12px;
    font-weight: 600;
    font-style: normal;
}

.button-grp button {
    display: flex;
    border: none;
    background-color: transparent;
    cursor: pointer;
    line-height: 2.5;       /* button needs special value for line-height */

}

.button-grp h2 {
    font-size: 12px;
    font-weight: 600;
    font-style: normal;
}

/* styling books list */
.cards {
    position: absolute;
    left: 350px;
}

.cards > small {
    background-color: #dfdcdc;
    width: 1000px;
    padding: 10px 0;
    justify-content: center;
    display: flex;
    color: #21282d;
    margin-top: 30px;
}

.cards small a:hover {
    text-decoration: underline;
}

.page {
    display: none;
    margin-top: 20px;
    padding: 20px;
    background-color: #fff;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.3);
    width: 1000px;   /* specify width and height of a container */
    height: 430px;
}

.page.active {
    display: block;
}


.price-books {
    font-family: Lato,sans-serif;
    font-size: 16px;
    font-weight: 700;
    font-style: normal;
    color: black;
}

table tr small a, figcaption p small a, .other-page a, .best-books a, .button-grp a, .button-grp button {
    color: #347d56;

}

table tr a:hover, figcaption p small a:hover, .best-books a:hover, .button-grp a:hover, .button-grp button:hover, .other-page a:hover, .term-use a:hover {
    text-decoration: underline;

}

main table td:nth-child(2) {
    padding-left: 200px;
    
}

main table {
    border-collapse: collapse; 
    
}

main table td {
    border-bottom: 0.5px solid gray;
    
}

main table td:last-child {
    padding-left: 300px;
    
}

main table td:last-child p {
    display: none;
}



figure {
    padding-top: 20px;
    
}

.figures {
    padding: 20px;
    background-color: #fff;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.3);
    width: 1000px;   /* specify width and height of a container */
    height: 430px;
    position: relative;
    right: 2%;
    margin-top: 80px;
}


figcaption {
    display: inline-block;
    width: 50%;
    margin-left: 50px;
    line-height: 25px;
    text-align: left;
}

figcaption a {
    color: #1a0dab;
}

figcaption h3:hover {
    text-decoration: underline;
}


.desc {
    color: #4d5156;
    margin-top: 2px;
    margin: 10px 10px 20px 0;
}

.pre-more {
    color: #4d5156;
    border: 1px solid rgb(232, 232, 232);
    border-radius: 20px;
    margin-right: 10px;
    font-size: 14px;
    font-weight: 400;
    padding: 10px;
    
}

.pre-order {
    border: 2px solid transparent;
    border-radius: 5px;
    padding: 8px 30px;
    background-color: #3d6db5;;
    color: white;
    position: absolute;
    left: 78%;
    top: 80%;
    font-family: Lato, sans-serif;
    font-size: 12.9973px;
}

.pre-order:hover {
    filter: brightness(0.8);
}

.pre-more:hover {
    background-color: rgb(245, 245, 245);
    cursor: pointer;
}

smll-author:hover {
    text-decoration: underline;
}

.author span a:hover {
    text-decoration: underline;
}

/* style other pages for books */
.other-page {
    margin-top: 50px;
    margin-left: 25em;

}

.best-books {
    color: #21282d;;
    font-family: Lato, sans-serif;
    font-size: 12.185px;
    line-height: 21.933px;
    font-weight: 400;
    font-style: normal;
    margin-top: 50px;
    border: 1px solid rgb(169, 169, 169);
    padding: 30px;
    position: absolute;
    left: 0%;
}

.best-books ul li{
    list-style-type: disc;
}

.best-books h2 {
    margin-top: 20px;
    margin-bottom: 5px;
}

.best-books ul {
    margin-left: 40px;
}


/* styling footer */
footer {
    position: relative;
    width: 100%;
    height: 380px;
}

footer table {
    margin-top: 20px;
    width: 95%;
    line-height: 30px;
    text-align: left;
    font-family: Lato, sans-serif;
    font-size: 12px;
    font-weight: 400;
    color:  #3e5962;
    margin-left: 60px;
    margin-bottom: 100px;
}


footer table td > a, .term-use a {
    font-family: Lato, sans-serif;
    font-size: 12px;
    font-weight: 400;
    color:  #3e5962;
}

footer table .font-subt {
    font: 600 12px/20px Lato, sans-serif;       /* font: font-weight font-size line-height font-family  */
}



footer table ul li {
    display: inline-block;
    margin-right: 10px;
}

footer i {
    color: white;
    border: 1px solid transparent;
    padding: 5px;
    border-radius: 50%;
    background-color: black;
}

footer i:hover {
    color: black;
    background-color: white;
    transition: 0.3s ease;
    border: 1px solid black;
}

.term-use {
    display: flex;
    margin-left: 60px;
    padding: 20px 0;
    margin-bottom: 20px;
}

.term-use li {
    margin-right: 40px;
}



/* Back-page links */
.cta {
    position: fixed;
    z-index: 3;
    top: 90%;
    left: 4%;
    display: flex;
    padding: 10px 15px;
    text-decoration: none;
    font-family: 'Poppins', sans-serif;
    font-size: 15px;
    color: white;
    width: 5%;
    align-items: center;
    text-align: center;
    justify-content: center;
    background: #6225e6;
    transition: 1s;
    box-shadow: 6px 6px 0 black;
    transform: skewX(-15deg);
}

.cta:focus {
    outline: none;
}

.cta:hover {
    transition: 0.5s;
    box-shadow: 10px 10px 0 #fbc638;
    
}

.wrapper span {
    transform: skewX(15deg);
}