$light-background: #f2ece4;
$light-text: #036;
$dark-background: #6b717f;
$dark-text: #d2e1dd;
@mixin theme-colors($light-theme: true) {
  @if $light-theme {
    background-color: $light-background;
    color: $light-text;
  } @else {
    background-color: $dark-background;
    color: $dark-text;
  }
}
.banner {
  @include theme-colors($light-theme: true);
  body.dark & {
    @include theme-colors($light-theme: false);
  }
}@mixin avatar($size, $circle: false) {
  width: $size;
  height: $size;
  @if $circle {
    border-radius: $size / 2;
  }
}
.square-av { @include avatar(100px, $circle: false); }
.circle-av { @include avatar(100px, $circle: true); }<ht<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body>
</body>
</html>!<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>AJAX = Asynchronous JavaScript And XML.h1 {
    height: 500px;
    height: 100vh;
}h1 {
    transform: translateY(-50%);
}h1 {
    font-size: 7vw;
}.box {
  width: 50vw;
  height: 100vh;
  background: gray;
  color: white;
}