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<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
/* Variable declarations */ 
:root {
  --blue: #1e90ff;
  --white: #ffffff; 
}
.container {
  --fontsize: 25px;
}
/* Styles */ 
body {
  background-color: var(--blue);
}
h2 {
  border-bottom: 2px solid var(--blue);
}
.container {
  color: var(--blue);
  background-color: var(--white);
  padding: 15px;
  font-size: var(--fontsize);
}
@media screen and (min-width: 450px) {
  .container {
    --fontsize: 50px;
  }
}
</style>
</head>
<body>
<h1>Using Variables in Media Queries</h1>
<div class="container">
  <h2>Lorem Ipsum</h2>
  <p>When the browser's width is less than 450px, the font-size of this div is 25px. When it is 450px or wider, set the --fontsize variable value to 50px. Resize the browser window to see the effect.</p>