.flip-card-front {
    background: url(images/coral.png);
    background-position: left top;
    background-repeat: repeat;
    z-index: 1;
  }
  
.flip-card-back {
    /* background: url(images/paper.png); */
    background-color: cadetblue;
    transform: rotateY(180deg);
    -webkit-transform: rotateY(180deg);
    z-index: 2;
}