<div id="block"></div>
#block {
  width: 20px;
  height: 20px;
  margin: 0 auto;
  background-color: blue;
  box-shadow: 
    20px 0 gray,
    -20px 0 gray;
}
/**
 Part of the "Creating Pixel Art with CSS" series by Jacque Schrag.
 Read the post: https://dev.to/jnschrag/creating-pixel-art-with-css-3451
**/

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