#demo{
  font-size:0;
}
#demo a{
  display:inline-block;
  width:20%;
  aspect-ratio: 1 / 1;
  overflow:hidden;
  position:relative;
  left:0;
  top:0;
}
#demo img{
  position:absolute;
  left:0;
  bottom:0;
  width:100%;
}