Check out example codes for "css animated background". It will help you in understanding the concepts better.

Code Example 1

/* Answer to: "css animated background" */

  Here are some awesome websites you can use that has many Animated
  Backgrounds that you can use!

  You don't want to copy someone's elses animated background?
  Feel free to learn how to make your own! W3Schools has a tutorial
  CSS animation and it's very easy to learn how to make one
  using their step-by-step guide!

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