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<p>
  Big spoilers below! Hover to reveal...
</p>
<p class="spoiler">
  Turns out he was dead the whole time. That guy is totally his father and the princess is his sister. They're all allergic to water and everything happens for a reason. He's the chosen one now, but he wasn't the first. What he thought was an alien planet was actually Earth. They turn the humans against each other to make the invasion easier. What you thought were flashbacks actually take place in the future. The simulations were real.
</p>
<p>
  End spoilers. Now you know everything.
</p>
@import url(http://fonts.googleapis.com/css?family=Arimo|Fjalla+One);

*, *::before, *::after {
  box-sizing: border-box;
}

body {
  padding: 0 10%;
  font: 24px/1.5 'Arimo', sans-serif;
  color: #55657a;
  background-color: #fff;
}

p {
  text-align: justify;
}

.spoiler {
  position: relative;
  color: transparent;
  text-shadow: 0 0 20px #55657a;
  cursor: help;
}

.spoiler::before, .spoiler::after {
  display: block;
  position: absolute;
  line-height: 1;
  font-family: 'Fjalla One', sans-serif;
  color: #872e27;
  text-align: center;
  text-shadow: none;
}

.spoiler::before {
  top: 36px;
  left: 0;
  right: 0;
  font-size: 72px;
  content: 'SPOILER ALERT';
}

.spoiler::after {
  opacity: 0;
  top: 84px;
  left: calc(50% - 36px);
  width: 60px;
  font-size: 60px;
  line-height: 72px;
  text-align: center;
  clip: rect(0, 72px, 72px, 0);
  content: '3 2 1';  
}

.spoiler:hover {
  color: #55657a;
  text-shadow: 0 0 0 transparent;
  transition: all 1s;
  transition-delay: 4s;
}

.spoiler:hover::before {
  animation: countdown-before 5s forwards;
}

.spoiler:hover::after {
  animation: countdown-after 5s forwards;
}

@keyframes countdown-before {
  25% {
    transform: translateY(-24px);
  }
  75% {
    opacity: 1;
  }
  100% {
  	opacity: 0;
    transform: translateY(-24px);
  }
}

@keyframes countdown-after {
  25% {
    opacity: 1;
    clip: rect(0, 72px, 72px, 0);
    transform: translateY(0);
    animation-timing-function: steps(1, start);
  }
  50% {
    clip: rect(72px, 72px, 144px, 0);
    transform: translateY(-72px);
    animation-timing-function: steps(1, start);
  }
  75% {
    opacity: 1;
    clip: rect(144px, 72px, 216px, 0);
    transform: translateY(-144px);
  }
  100% {
    opacity: 0;
    clip: rect(144px, 72px, 216px, 0);
    transform: translateY(-144px);
  }
}
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