body {
    background-color: #f5f5f5;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 100vw;
    height: 100vh;
    margin: 0;
    padding: 0;
    display: flex;
    position: relative;
}

#container {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100vw;
    height: 100vh;
    background-color: rgb(226, 231, 229);
}

#show-iframe {
    display: block;
    background-color: #fff;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    overflow: hidden;
}

.iframe-epub {
    display: block;
    width: 1920px;
    height: 1080px;
    transform-origin: 0px 0px;
    border: none;
    overflow: hidden;
}


.navigation-button {
    cursor: pointer;
    position: absolute;
    border-radius: 100;
    z-index: 100;
    bottom: 10vw;
    opacity: 0.2;
}

.navigation-button img {
    width: 60px;
    height: 60px;
}

.next {
    right: 3vw;
}

.prev {
    left: 3vw;
}

.prev img {
    transform: rotate(180deg);
}

#bt12 {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: #3498db;
    color: #fff;
    border: none;
    border-radius: 50%;
    width: 60px;
    height: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    user-select: none;
    z-index: 100;
}