CSS

По клику меняется цвет фона и текстовое содержимое. Без js.

by akogch

HTML

<input type="checkbox" />

<div class="section-1">
  <h1>Don't click anywhere!</h1>
  <h3>(By the way, are you using a webkit browser?)</h3>
  <p>You never know what <strong>will happen.</strong></p>
</div>

<div class="section-2">
  <h1>Well, looks like you clicked.</h1>
  <h3>
    Your parents must have been mad at you more than you think when you were a
    child! ;)
  </h3>
  <p>
    Hope you enjoy your time here. <strong>You can always click back.</strong>
  </p>
</div>

SCSS

* {
  -webkit-font-smoothing: antialiased;
}

@mixin section {
  z-index: 10;
  position: fixed;
  height: 100%;
  width: 100%;
  top: 0;
  pointer-events: none;
  padding: 40px;
  font-family: Helvetica, Arial;
}

html {
  height: 100%;
  margin: 0;
}

body {
  height: 100%;
  width: 100%;
  margin: 0;
}

input[type=checkbox] {
  -webkit-appearance: none;
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
  outline: none;
  border: none;
  display: block;
  background-color: tomato;
  transition: background-color 1s;
  &:checked {
    background-color: white;
    transition: background-color 1s;
    &~.section-2 {
      display: block;
    }
    &~.section-1 {
      display: none;
    }
  }
}

.section-1 {
  display: block;
  color: white;
  @include section;
}

.section-2 {
  display: none;
  color: tomato;
  @include section;
}