body {
  margin: auto;
  background-color: #7F00FF;
  background-image: -webkit-linear-gradient(to right, #E100FF, #7F00FF);
  background-image: linear-gradient(to right, #E100FF, #7F00FF);

}
.center {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}
img {   
  opacity: 1; 
  transition: opacity 0.5s ease;
}
img:hover { 
  opacity: 0.7;
}