.square_blocks_icon {
    width: 100%;
    height: 77px;
    position: relative;
    display: block;
    margin: auto;
}
.square_blocks_icon img {
    position: absolute;
    top: 50%;
    left: 0;
    right: 0;
    margin: auto;
    -webkit-transform: translateY(-50%);
    -moz-transform: translateY(-50%);
    -o-transform: translateY(-50%);
    transform: translateY(-50%);
    opacity: 0;
}
.square_blocks_icon img:nth-child(1) {
    opacity: 1;
}