html, body {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  overflow: hidden;
}

.parent {
  width: 100%;
  height: 100%;
  position: fixed;
  top: 0;
  left: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: auto;   
}

.block {
  background: #60a839;
  width: 100%;
}

.block img {
  display: block;
  border: none;
  width: 100%;
}