.calc_loader {
  border: 16px solid #f3f3f3;
  border-radius: 50%;
  border-top: 16px solid #3498db;
  width: 120px;
  height: 120px;
  -webkit-animation: spin 2s linear infinite; /* Safari */
  animation: spin 2s linear infinite;
}

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

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


.flip-card {
  background-color: transparent;
  max-width: 500px;
  height: 300px;
  /* perspective: 1000px; */
}

.flip-card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  transition: transform 0.6s;
  transform-style: preserve-3d;
  /* box-shadow: 0 4px 8px 0 rgba(0,0,0,0.2); */
}

.flip-card:focus .flip-card-inner {
  transform: rotateY(180deg);
}

.flip-card-front, .flip-card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
}

.flip-card-front {

/*
  background-color: #bbb;
  color: black;
*/
}

.flip-card-back {
/*
  background-color: #2980b9;
  color: white;
*/
  transform: rotateY(180deg);
}