A modern website contains thousands of lines of styles. Styles for blocks, text, and small areas are often all in one place. Imagine this: there's a certain shade of red that we use in lots of different blocks.

How convenient would it be to change all the values if you want to change the base color? That's right - we would have to find all the values within the file and replace them with new ones.

This has been one of the main problems with CSS for a long time. With the advent of the CSS3 standard, this problem has gone thanks to variables.

Variables in programming are a small area of memory in which we store the desired value. This value can always be accessed from any available location.

As in programming, in CSS, you can specify variables that will be available throughout site development. If variables are used, you can quickly replace some values with other values instead of having to replace property values manually.

A variable is created using the --variable-name construct. You can choose the name of the variable yourself. As an example, let's create a variable called --main-color that contains the base color of the pages. Set it to be black:

--main-color: #000000;

This simplicity hides the fact that variables have different scopes, areas of the file from which they can be used. This is a big topic, so let's talk only about global scope for now. This will allow a variable to be used in any area of the CSS file.

To create a global variable, you need to specify it in a special construct, :root. This is usually done at the beginning of the CSS file:

:root {
  --main-color: #000000;
}

You can now use a variable in any part of our CSS code. This is done with a special construction, var(--variable-name).

:root {
  --main-color: #000000;
}

.news-block {
  background-color: var(--main-color);
}

.left-sidebar {
  background-color: var(--main-color);
}

If we want to set a different shade of black, just change the value of the -main-color variable, and all changes will automatically apply to blocks with the .news-block and .left-sidebar classes

Create a variable called --main-blue and set its value to the color blue #00bfff. Declare the variable in :root. Write the styles in the <style> tag