body {
    background-color: #f3f3f3;
}

.header-logo img {
    filter: brightness(0) invert(1);
    height: 4vh;
}

#toolbar-top,
#toolbar-bottom {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100vw;
    z-index: 100;
}

#toolbar-top {
    top: 0;
    height: 6vh;
    margin-bottom: 1vh;
    background-color: black;
}

#toolbar-bottom {
    bottom: 0;
    margin-top: 2vh;
    height: 6vh;
}

.btn-move {
    font-size: 3vh;
    padding: .1vh .45vh;
    background: none;
    color: #222;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all .4s;
    cursor: pointer;
    border: none;
    margin: 0 1rem;
}

button:hover {
    color: #909090;
}

.btn-download {
    background: none;
    font-size: 2.5vh;
    width: 50px;
    padding: .5vh 0;
    display: flex;
    justify-content: center;
    align-items: center;
    color: #333;
    font-weight: bold;
    text-decoration: none;
    border-radius: .25vh;
    transition: all .4s;
    letter-spacing: .15rem;
    margin: 0 .25rem;
}

.btn-download:hover {
    color: #797979;
}

#btn-sound {
    width: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 2.5vh;
    font-weight: bold;
    transition: all .4s;
    background: none;
    border: none;
    color: #222;
    cursor: pointer;
    margin: 0 .25rem;
}

#btn-sound:hover {
    filter: brightness(.8);
}

#prev-page {
    font-size: 1.2vh;
}

.page-counter {
    color: #555;
    font-size: 2.5vh;
}

.page-current {
    font-weight: 600;
    color: #111;
}

.flip-book {
    box-shadow: 0 0 20px 0 rgba(0, 0, 0, 0.1);
    display: none;
    background-size: cover;
    max-height: 100vh;
    overflow: hidden;
}

.page {
    overflow: hidden;
}

.page .page-content {
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: stretch;
}

.page-content img {
    width: 100%;
}

.page .page-content .page-header {
    height: 30px;
    font-size: 100%;
    text-transform: uppercase;
    text-align: center;
}

.page .page-content .page-image {
    height: 100%;
    background-size: contain;
    background-position: center center;
    background-repeat: no-repeat;
}

.page .page-content .page-text {
    height: 100%;
    flex-grow: 1;
    font-size: 80%;
    text-align: justify;
    margin-top: 10px;
    padding-top: 10px;
    box-sizing: border-box;
    border-top: solid 1px hsl(35, 55, 90);
}

.page .page-content .page-footer {
    height: 30px;
    border-top: solid 1px hsl(35, 55, 90);
    font-size: 80%;
    color: hsl(35, 20, 50);
}

.page.--left::before {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 20px;
    /* 그림자 넓이 조절 가능 */
    height: 100%;
    pointer-events: none;

    /* 오른쪽 경계에서 왼쪽 방향으로 짙은 검정에서 투명으로 */
    background: linear-gradient(to left, rgba(0, 0, 0, 0.2), rgba(0, 0, 0, 0));
}

.page.--right::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 20px;
    /* 그림자 넓이 조절 가능 */
    height: 100%;
    pointer-events: none;

    /* 왼쪽 경계에서 오른쪽 방향으로 짙은 검정에서 투명으로 */
    background: linear-gradient(to right, rgba(0, 0, 0, 0.2), rgba(0, 0, 0, 0));
}



.page.--right .page-content .page-footer {
    text-align: right;
}

/* Hard pages */
.page.hard {
    background-color: hsl(35, 50, 90);
    border: solid 1px hsl(35, 20, 50);
}

/* Cover pages */
.page.page-cover {
    background-color: hsl(35, 45, 80);
    color: hsl(35, 35, 35);
    border: solid 1px hsl(35, 20, 50);
}

.page.page-cover h2 {
    text-align: center;
    padding-top: 50%;
    font-size: 210%;
}

.page.page-cover.page-cover-top {
    box-shadow: inset 0px 0 30px 0px rgba(36, 10, 3, 0.5), -2px 0 5px 2px rgba(0, 0, 0, 0.4);
}

.page.page-cover.page-cover-bottom {
    box-shadow: inset 0px 0 30px 0px rgba(36, 10, 3, 0.5), 10px 0 8px 0px rgba(0, 0, 0, 0.4);
}

.stf__parent {
    position: relative;
    display: block;
    box-sizing: border-box;
    transform: translateZ(0);
    -ms-touch-action: pan-y;
    touch-action: pan-y;
}

.page-container {
    display: flex;
    justify-content: center;
    align-items: center;
    padding-right: 15px;
    padding-left: 15px;
    overflow: hidden;
    min-height: 70vh;
}