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<!DOCTYPE html>
<html>
<head>
<style>
:root {
  --blue: #1e90ff;
  --white: #ffffff; 
}
body {
  background-color: var(--blue);
}
h2 {
  border-bottom: 2px solid var(--blue);
}
.container {
  color: var(--blue);
  background-color: var(--white);
  padding: 15px;
}
.container button  {
  background-color: var(--white);
  color: var(--blue);
  border: 1px solid var(--blue);
  padding: 5px;
}
</style>
<script>
// Get the root element
var r = document.querySelector(':root');
// Create a function for getting a variable value
function myFunction_get() {
  // Get the styles (properties and values) for the root
  var rs = getComputedStyle(r);
  // Alert the value of the --blue variable
  alert("The value of --blue is: " + rs.getPropertyValue('--blue'));
}
// Create a function for setting a variable value
function myFunction_set() {