mystyle.scss
mystyle.css
mypage.html
 
/* Define standard variables and values for website */
$bgcolor: lightblue;
$textcolor: darkblue;
$fontsize: 18px;

/* Use the variables */
body {
  background-color: $bgcolor;
  color: $textcolor;
  font-size: $fontsize;
}                  
body {
  background-color: lightblue;
  color: darkblue;
  font-size: 18px;
}                  
<!DOCTYPE html>
<html>
<link rel="stylesheet" href="mystyle.css">
<body>

<h1>Hello World</h1>

<p>This is a paragraph.</p>

</body>
</html>