<div class="container">
  <span class="text -smooth">
    Toggle "-smooth" class to see the difference. The smooth version precisely reflects the browser fonts, making them look exactly how you see them in the Sketch App. 
  </span>
</div>

.-smooth {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale; 
}

.text {
  font-size: 18px;
  line-height: 1.5em;
  font-family: 'Source Sans Pro', sans-serif;
  color: #fff;
}

.container {
  height: 100%;
  padding: 52px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-sizing: border-box;
}

html, body {
  height: 100%;  
}

body {
  background-color: #1D1F20;
}