:root {
    /* Global variables */
    --doddle-gray: #444444;
    --doddle-font: "Roboto", sans-serif;
    --doddle-orange: #ff6600;
    --doddle-white: #ffffff;
}

body {
    color: var(--doddle-gray);
    font-family: var(--doddle-font);
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
}

.main {
    background-color: var(--doddle-gray);
    border-style: none;
    position: relative;
    margin: 0;
    padding: 0 0 20px 0;
    min-height: 100vh;
}

.content {
    text-align: center;
    position: relative;
    padding: 10px;
}

.interface button i {
    font-size: 2.5rem;
    font-weight: bold;
}

.interface button {
    background-color: var(--doddle-orange);
    border-radius: 10px;
    border-style: none;
    color: var(--doddle-white);
    font-size: 1.5rem;
    font-weight: bold;
    width: 80px;
    height: 50px;
    margin-left: 10px;
    margin-top: 10px;
    transition: 0.1s;
    text-transform: capitalize;
    box-shadow: 3px 3px 3px 3px black;
}

.interface button:hover {
    background-color: var(--doddle-gray);
    cursor: pointer;
    box-shadow: 0px 0px 0px 0px;
    border: 1px solid black;
}

.interface {
    display: flex;
    justify-content: flex-end;
}

.screen {
    background-color: var(--doddle-white);
    border-radius: 10px;
    padding: 50px 50px 25px 50px;
    margin: 5px auto;
}

.help-text {
    background-color: var(--doddle-white);
    color: var(--doddle-orange);
    border-style: solid;
    border-width: 3px;
    border-color: var(--doddle-gray);
    border-radius: 5px;
    bottom: 20vh;
    right: 5vw;
    width: 25rem;
    box-shadow: 5px 5px 5px 5px black;
    font-family: var(--doddle-font);
    font-size: 1.5rem;
}

.help-text p {
    margin: 10px;
}

.startPanel {
    background-color: var(--doddle-white);
    border-radius: 5px;
    border-color: var(--doddle-gray);
    border-width: 3px;
    border-style: solid;
    font-size: 1.5rem;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    box-shadow: 10px 10px 10px 0px black;
    padding: 50px;
}

.startPanel p {
    text-align: center;
    vertical-align: middle;
}

.intro img {
    width: 600px;
}

.heading {
    color: var(--doddle-gray);
    text-align: center;
    text-transform: capitalize;
}

.intro,
.help-text,
.startPanel {
    position: absolute;
}

/* Content_________________________________________________________________ */
.book-container {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 2em 0;
    background: url(images/study-room.jpg);
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}

.book {
    transition: opacity 0.4s 0.2s;
}

.pages h2 {
    color: black;
    background-color: var(--doddle-white);
    padding: 10px;
    margin: 20px auto;
    text-align: center;
    line-height: 2;
    /* font-size: 1.8rem; */
    font-size: 1.9em;
}

.book .page:nth-child(8) h2 {
    color: palevioletred;
    margin-top: 90%;
}

.pages p {
    margin-top: 5vh;
    text-align: left;
    /* font-size: 1.2rem; */
    font-size: 1.5em;
    color: var(--doddle-gray);
}

.pages figure {
    font-size: 1.5em;
    text-align: justify;
    margin: 0;
    width: 100%;
}

.pages li {
    width: 100%;
    text-align: left;
}

.no-bullet {
    list-style-type: none;
}

.yellow {
    background-color: yellow;
    padding: 5px;
}

.lightblue {
    margin-top: 3vh;
    background-color: lightskyblue;
    padding: 5px;
    transform: translateX(-6%);
}

.bordered{
    border: 2px solid goldenrod;
    font-family: var(--doddle-font);
    text-align: left;
    padding: 20px;
    font-size: 1.3em;
}

.dark{
    font-weight: bold;
}

.page {
    width: 10vw;
    height: 24vw;
    background-color: #111111;
    float: left;
    margin-bottom: 0.5em;
    background: left top no-repeat;
    background-size: cover;
    padding: 20px;
    position: relative;
    font-size: 16px;
}

.page:nth-child(even) {
    clear: both;
}

.book {
    perspective: 250vw;
}

.book .pages {
    width: 60vw;
    height: 44vw;
    position: relative;
    transform-style: preserve-3d;
    backface-visibility: hidden;
    border-radius: 4px;
}

.book .page:nth-child(2),
.book .page:nth-child(3),
.book .page:nth-child(4),
.book .page:nth-child(5),
.book .page:nth-child(6),
.book .page:nth-child(7)
{
    border: 5px solid purple;
}

.book .page:nth-child(1), .book .page:nth-child(8) {
    background-color: purple;
}

.book .page:nth-child(1){
    border-left: 20px solid black;
}
.book .page:nth-child(8){
    border-right: 20px solid black;
}

.book .page:nth-child(1) img {
    width: 80%;
    height: 50%;
    margin-top: 15%;
}

.book .page:nth-child(2) img {
    width: 100%;
    position: absolute;
    bottom: 0;
    left: 0;
}

.book .page {
    float: none;
    clear: none;
    margin: 0;
    position: absolute;
    top: 0;
    width: 30vw;
    height: 44vw;
    transform-origin: 0 0;
    transition: transform 1.4s;
    backface-visibility: hidden;
    transform-style: preserve-3d;
    cursor: pointer;
    user-select: none;
    background-color: #f0f0f0;
}

.book .page:before {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0);
    transition: background 0.7s;
    z-index: 2;
}

.book .page:nth-child(odd) {
    pointer-events: all;
    /* pointer-events: none; */
    transform: rotateY(0deg);
    right: 0;
    border-radius: 0 4px 4px 0;
    background-image: linear-gradient(to right, rgba(0, 0, 0, .15) 0%, rgba(0, 0, 0, 0) 10%);
}

.book .page:nth-child(odd):hover {
    transform: rotateY(-15deg);
}

.book .page:nth-child(odd):hover:before {
    background: rgba(0, 0, 0, 0.03);
}

.book .page:nth-child(odd):before {
    background: rgba(0, 0, 0, 0);
}

.book .page:nth-child(even) {
    pointer-events: none;
    transform: rotateY(180deg);
    transform-origin: 100% 0;
    left: 0;
    border-radius: 4px 0 0 4px;
    border-color: black;
    background-image: linear-gradient(to left, rgba(0, 0, 0, .12) 0%, rgba(0, 0, 0, 0) 10%);
}

.book .page:nth-child(even):before {
    background: rgba(0, 0, 0, 0.2);
}

.book .page.grabbing {
    transition: none;
}

.book .page.flipped:nth-child(odd) {
    pointer-events: none;
    transform: rotateY(-180deg);
}

.book .page.flipped:nth-child(odd):before {
    background: rgba(0, 0, 0, 0.2);
}

.book .page.flipped:nth-child(even) {
    pointer-events: all;
    transform: rotateY(0deg);
}

.book .page.flipped:nth-child(even):hover {
    transform: rotateY(15deg);
}

.book .page.flipped:nth-child(even):hover:before {
    background: rgba(0, 0, 0, 0.03);
}

.book .page.flipped:nth-child(even):before {
    background: rgba(0, 0, 0, 0);
}

*,
* :before,
*:after {
    box-sizing: border-box;
}


.page:nth-child(odd) {
    background-position: right top;
}

@media screen and (max-width: 1330px) {
    .page{
        /* font-size: 12px; */
        font-size: 14px;
    }
}

@media screen and (max-width: 1205px) {
    .page{
        font-size: 12px;
    }
}

@media screen and (max-width: 1050px) {
    .page{
        font-size: 10px;
    }
}

/* @media screen and (max-width: 820px) { */
@media screen and (max-width: 910px) {
    .page{
        font-size: 8px;
    }
}

/* @media screen and (max-width: 710px) { */
@media screen and (max-width: 790px) {
    .page{
        font-size: 6px;
    }
}

@media screen and (max-width: 650px) {
    .page{
        font-size: 4px;
    }
}

@media screen and (max-width: 510px) {
    .page{
        font-size: 2px;
    }
}

@media screen and (max-width: 400px) {
    .page{
        font-size: 1px;
    }
}