Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="laptop-container">
    <img src="http://placehold.it/640x360/3333cc/ffffff" alt="" />
</div>

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

* {
  box-sizing: border-box;
}

body {
  text-align: center;
}

.laptop-container {
    display: inline-block;
    position: relative;
    padding: 2px;
    margin: 2%;
    border: 4px solid #ccc;
    border-radius: 4px;
    
    img {
      vertical-align: top;
    }
    
    &::after {
      content: '';
      display: block;
      position: absolute;
      width: 110%;
      height: 20px;
      left: -5%;
      bottom: -20px;
      background: #ccc;
      border-radius: 10px;
    }
}

SassMeister-output.css

* {
  box-sizing: border-box;
}

body {
  text-align: center;
}

.laptop-container {
  display: inline-block;
  position: relative;
  padding: 2px;
  margin: 2%;
  border: 4px solid #ccc;
  border-radius: 4px;
}

.laptop-container img {
  vertical-align: top;
}

.laptop-container::after {
  content: '';
  display: block;
  position: absolute;
  width: 110%;
  height: 20px;
  left: -5%;
  bottom: -20px;
  background: #ccc;
  border-radius: 10px;
}

SassMeister-rendered.html

<div class="laptop-container">
    <img src="http://placehold.it/640x360/3333cc/ffffff" alt="" />
</div>