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HTML

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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HTML 

              
                <div class="message">
  &check; Made by <a href="https://codepen.io/pieter-biesemans/" target="_blank" title="&check; check out my other work">Pieter Biesemans</a> with &#9749;, &#128420; &amp; &#8986;</i>
</div>

<div class="wrapper">
  <div class="score left"></div>
  <div class="paddle left"></div>
  <div class="middle"></div>
  <div class="paddle right"></div>
  <div class="score right"></div>
  <div class="ball"></div>
  
</div>
!

CSS 

              
                @import url('https://fonts.googleapis.com/css?family=Press+Start+2P');

div{
  position: absolute;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  overflow: visible;
}

body{
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  margin: 0;
  padding: 0;
  color: white;
  font-family: 'Press Start 2P', cursive;
  font-size: 1vmin;
  background: black;
  
  & .wrapper{
    top: 50%;
    left: 50%;
    width: 75vmin;
    height: 75vmin;
    transform: translate(-50%, -50%);
    
    & .middle{
      top: 50%;
      left: 50%;
      width: 1vmin;
      height: 100%;
      border-right: 1vmin dashed white;
      transform:translate(-50%, -50%) rotate(0deg);
      transform-origin: center center;
      animation: middle 10s 0s ease alternate infinite;
    }
    
    & .paddle{
      top: 0;
      width: 50%;
      height: 25%;
      transform:translatY(0) rotate(0deg);
      &.left{
        left: 0;
        border-left: 1vmin solid white;
        transform-origin: right center;
        animation: paddleleft 10s 0s ease alternate infinite;
      }
      &.right{
        right: 0;
        border-right: 1vmin solid white;
        transform-origin: left center;
        animation: paddleright 10s 0s ease alternate infinite;
      }
    }
    
    & .ball{
      width: 1vmin;
      height: 1vmin;
      background: white;
      transform-origin: center center;
      animation: ball 10s 0s linear alternate infinite;
    }
    
    & .score{
      top: -10vmin;
      left: calc(50% - 12vmin);
      width: 10vmin;
      height: 10vmin;
      font-size: 8em;
      &:before{
        display: block;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        text-align: center;
      }
      &.left{
        left: calc(50% - 12vmin);
        &:before{
          content: '0';
          animation: scoreleft 10s 0s ease alternate infinite;
        }
      }
      &.right{
        left: calc(50% + 2vmin);
        &:before{
          content: '0';
          animation: scoreright 10s 0s ease alternate infinite;
        }
      }
    }
    
  }
  
  & .message{
    position: absolute;
    right:  0.5vw;
    bottom: 1vw;
    max-width: 90vw;
    font-size: 1.5em;
    color: white;

    & a{
      color: inherit;
      text-decoration: none;
      border-bottom: 1px solid #444;
      &:hover{
        border-width: 3px;
      }
    }

  }
  
}

@keyframes middle {
  0%   {height:100%;transform:translate(-50%,-50%) rotate(0deg);}
  20%  {height:100%;transform:translate(-50%,-50%) rotate(0deg);}
  30%  {height:100%;transform:translate(-50%,-50%) rotate(0deg);}
  40%  {height:75%;transform:translate(-50%,-50%) rotate(-90deg);}
  50%  {height:20%;transform:translate(-50%,-50%) rotate(-360deg);}
  60%  {height:60%;transform:translate(-50%,-50%) rotate(90deg);}
  70%  {height:50%;transform:translate(-50%,-50%) rotate(270deg);}
  80%  {height:10%;transform:translate(-50%,-50%) rotate(-90deg);}
  90%  {height:40%;transform:translate(-50%,-50%) rotate(90deg);}
  100% {height:90%;transform:translate(-50%,-50%) rotate(360deg);}
}

@keyframes ball {
  0%   {top:0;left:50%;width:1vw;}
  10%  {top:0;left:50%;width:1vw;}
  20%  {top:40%;left:100%;width:1vw;}
  30%  {top:80%;left:0%;width:1vw;}
  40%  {top:80%;left:100%;width:1vw;}
  50%  {top:0%;left:50%;width:1vw;}
  60%  {top:100%;left:50%;width:1vw;}
  70%  {top:50%;left:100%;width:1vw;}
  80%  {top:0%;left:50%;width:1vw;}
  90%  {top:50%;left:0%;width:1vw;}
  100% {top:50%;left:100%;width:1vw;}
}

@keyframes paddleleft{
  0%   {top:50%;height:25%;transform:translateY(0) rotate(0deg);}
  20%  {top:40%;height:25%;transform:translateY(0) rotate(0deg);}
  30%  {top:60%;height:25%;transform:translateY(0) rotate(0deg);}
  40%  {top:50%;height:25%;transform:translateY(-50%) rotate(0deg);}
  50%  {top:50%;height:45%;transform:translateY(-50%) rotate(90deg);}
  60%  {top:50%;height:65%;transform:translateY(-50%) rotate(180deg);}
  70%  {top:50%;height:15%;transform:translateY(-50%) rotate(-180deg);}
  80%  {top:50%;height:10%;transform:translateY(-50%) rotate(360deg);}
  90%  {top:50%;height:50%;transform:translateY(-50%) rotate(0deg);}
  100% {top:50%;height:5%;transform:translateY(-50%) rotate(-90deg);}
}

@keyframes paddleright{
  0%   {top:50;height:25%;transform:translateY(0) rotate(0deg);}
  20%  {top:30%;height:25%;transform:translateY(0) rotate(0deg);}
  30%  {top:40%;height:25%;transform:translateY(0) rotate(0deg);}
  40%  {top:80%;height:25%;transform:translateY(-50%) rotate(0deg);}
  50%  {top:50%;height:15%;transform:translateY(-50%) rotate(-180deg);}
  60%  {top:50%;height:5%;transform:translateY(-50%) rotate(90deg);}
  70%  {top:50%;height:65%;transform:translateY(-50%) rotate(270deg);}
  80%  {top:50%;height:10%;transform:translateY(-50%) rotate(-90deg);}
  90%  {top:50%;height:40%;transform:translateY(-50%) rotate(90deg);}
  100% {top:50%;height:95%;transform:translateY(-50%) rotate(0deg);}
}

@keyframes scoreleft{
  0%   {content:'0';}
  20%  {content:'0';}
  30%  {content:'0';}
  40%  {content:'0';}
  50%  {content:'?';}
  60%  {content:'wait';}
  70%  {content:'what?';}
  80%  {content:'eh';}
  90%  {content:':o';}
  100% {content:':~';}
}

@keyframes scoreright{
  0%   {content:'0';}
  20%  {content:'0';}
  30%  {content:'0';}
  40%  {content:'0';}
  50%  {content:'!';}
  60%  {content:'';}
  70%  {content:'';}
  80%  {content:'';}
  90%  {content:'';}
  100% {content:'';}
}
!

JS 

              
                /*
This Codepen is in the Public Domain.
You can use it for whatever purpose you like, except evil.
*/
!
999px

Console