img {
  max-width: 100%
}

.box {
  border: 3px solid;
  padding: 10px;
  font-size: 20px;
  text-align: center;
  margin-bottom: 10px;
  margin: 10px;
}
.white { 
  background: white;
}

.blue {
  background: blue;
}

body {
  background-color: gray;
  text-align: center;
}

@media (prefers-color-scheme: light) {
  .blue {
    background: lightblue;
  }
}