a {
  text-decoration: none;
  color: black;}

.button {
position:fixed;
width: 100px;
height: 100px;
background: magenta;
display:flex;
justify-content: center;
align-items: center;
top:50%;
transform:translateY(-50%);
transition: background .5s ease,            height 1s ease;
}

.button:hover {
  background: chartreuse;
  height:900px;
}

.prev {
left: 0;
}

.next {
right:0;
}


.image {
display:none;
position: fixed;
top: 50%;
right:50%;
transform: translate(45%,-50%);

}

.hover-img:hover .image {
display: block;
}