html,
body {
  margin: 0;
  width: 100%;
  min-height: 100%;
  background: #d9d9d9;
}

body {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.cover,
.cover img {
  display: block;
  width: 100%;
}

.cover img {
  height: auto;
}