html, body, #viewDiv {
    padding: 0;
    margin: 0;
    height: 97%;
    width: 100%;
  }

#top-header {
    width: 100%;
    background-image: linear-gradient(-90deg, red, yellow);
    color: black;
    text-align: center;
    font-weight: bolder;
    padding-top: 20px;
    padding-bottom: 20px;
    font-size: 20px;
}

.visible {
  display: block !important;
}

#loadingDiv{
  position: absolute;
  margin-top: 7vh;
  text-align: center;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
  background-color: black;
  color: white;
  display: none;
  opacity: 0.8;
}

#loadingDiv-content{
  position: relative;
  height: 100px;
  width: 100px;
  background-color: red;
  margin: auto;
  margin-top: 35vh;
  transform: rotate(45deg);
  animation: spin 2s infinite;
}

@keyframes spin {
  0%{
      transform: rotate(90deg);
  }
  25% {
      transform: rotate(180deg);
  }
  50%{
      transform: rotate(270deg);
  }
  100% {
      transform: rotate(360deg);
  }
}