Generated by SassMeister.com.

SassMeister-input-HTML.html

<ul class="icons">
  <li></li>
</ul>

SassMeister-input.scss

// ----
// Sass (v3.4.13)
// Compass (v1.0.3)
// ----

.icons {
  list-style: none;
  padding: 0;
  margin: 30px;

  li {
    outline: 1px solid red; // red outline on actual element
    position: absolute; // absolute positioning for the box shadow elements
    width: 20px; //width of pixel
    height: 20px; //height of pixel
    top: -20px;
    left: -20px;
    // box shadow positions the pixels and colors them:
    box-shadow: 20px 20px 0 hotpink, 40px 40px 0 hotpink, 60px 60px hotpink;
  }
}

SassMeister-output.css

.icons {
  list-style: none;
  padding: 0;
  margin: 30px;
}
.icons li {
  outline: 1px solid red;
  position: absolute;
  width: 20px;
  height: 20px;
  top: -20px;
  left: -20px;
  box-shadow: 20px 20px 0 hotpink, 40px 40px 0 hotpink, 60px 60px hotpink;
}

SassMeister-rendered.html

<ul class="icons">
  <li></li>
</ul>