.viewer {
    width: 100%;
    height: auto;
    margin: auto;
    overflow: hidden;
    position: relative;
}

.viewer img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: 6px;
    cursor: grab;
    transform: scale(1);
}

.viewer img:active {
    cursor: grabbing;
}

#preloader {
    text-align: center;
    padding: 20px;
}

.loader {
    display: none;
    position: absolute;
    top: calc(50% - 30px);
    left: calc(50% - 30px);
    transform: translate(-50%, -50%);
    border: 8px solid #f3f3f3;
    border-radius: 50%;
    border-top: 8px solid #3498db;
    width: 60px;
    height: 60px;
    -webkit-animation: spin 2s linear infinite;
    animation: spin 2s linear infinite;
}

@-webkit-keyframes spin {
    0% { -webkit-transform: rotate(0deg); }
    100% { -webkit-transform: rotate(360deg); }
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}