.center {
    text-align: center;
    display: block;
}

.container { 
    height: 90vh;
    position: relative;
    text-align: center;
  }
  
  .vertical-center {
    margin: 0;
    position: absolute;
    top: 50%;
    -ms-transform: translateY(-50%);
    transform: translateY(-50%);
  }