.img-responsive
{
  position: absolute;
  width: 100%;
  height: 100%;
  object-fit: contain;
  top: 0px;
  bottom: 0px;
  left: 0px;
  right: 0px;
}

.X
{
  position: fixed;
  bottom: 20px;
  left: 50%;
  z-index: 1000;
  margin: -25px 0px 0px -25px;
}

.avanti
{
  position: fixed;
  bottom: 20px;
  left: 65%;
  z-index: 1000;
  margin: -25px 0px 0px -25px;
}

.indietro
{
  position: fixed;
  bottom: 20px;
  left: 35%;
  z-index: 1000;
  margin: -25px 0px 0px -25px;
}