<div class="container">

  <h1>Highlight Color Change</h1>

  <p>Highlight this text to see the color change! I've set up an array that holds all the possible highlight colors in the JavaScript panel of this pen. When your mouse button is pressed, I grab the first color from that array and remove it by using shift(), apply that color to a CSS variable, and then push that color value to the bottom of the array. This allows me to have that infinite color rotation.
  </p>

  <p>
    The trick here is to use the ::selection selector. In this example, I set the background property equal to the CSS variable I set up and that is being controlled by the JavaScript. Pretty neat, huh?</p>

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</div>

:root {
  --highlight-color: null;
}

body {
  background: black;
  font-family: "Helvetica", sans-serif;
}

.container {
  width: 80%;
  min-height: 100vh;
  color: white;
  margin: 0 auto;
}

::selection {
  background: var(--highlight-color);
}

const colors = ["#c1b001", "#a8140e", "#4315aa", "#359d09", "#8f4762"];

window.addEventListener("mousedown", (e) => {
  const color = colors.shift();
  document.documentElement.style.setProperty("--highlight-color", color);
  colors.push(color);
});