To create a CSS variable, you just need to give it a name with two hyphens in front of it and assign it a value like this:
--penguin-skin: gray;
This will create a variable named --penguin-skin and assign it the value of gray. Now you can use that variable elsewhere in your CSS to change the value of other properties to gray.
Challenge: In the penguin class, create a variable name --penguin-skin and give it a value of gray.
