html,
body {
  margin: 0;
  padding: 0;
}

body {
  background-color: red;
  color: white;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  background: radial-gradient(#ff7744, #ff0044);
}

* {
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  -moz-osx-font-smoothing: grayscale;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
}

.start {
  -webkit-transition: opacity 1.0s ease-in-out;
  -moz-transition: opacity 1.0s ease-in-out;
  transition: opacity 1.0s ease-in-out;
  opacity: 0;
}
.middle {
  -webkit-transition: opacity 1.0s ease-in-out;
  -moz-transition: opacity 1.0s ease-in-out;
  transition: opacity 1.0s ease-in-out;
  opacity: 1;
}
.end {
  -webkit-transition: opacity 1.0s ease-in-out;
  -moz-transition: opacity 1.0s ease-in-out;
  transition: opacity 1.0s ease-in-out;
  opacity: 0;
}