Customize your CSS with CSS Custom Properties: use variables to store values and apply them across your stylesheets.

CSS Custom Properties, also known as CSS variables, are a powerful tool in CSS that allow you to define a value once and reuse it throughout your stylesheet.

This can greatly simplify your code and make it easier to maintain.

To define a custom property, you use the `–` prefix followed by a name and a value.

For example:

css
 :root {
   --primary-color: #007bff;
 }

This defines a custom property called `–primary-color` with a value of `#007bff`.

You can then use this custom property anywhere in your stylesheet by referencing it with the `var()` function.

For example:

css
 a {
   color: var(--primary-color);
 }

This sets the color of all links to the value of `–primary-color`, which in this case is `#007bff`.

Custom properties can also be inherited and overridden just like any other CSS property.

For example:

css
 .container {
   --bg-color: #ffffff;
 }

.card {
   background-color: var(--bg-color);
 }

.card-secondary {
   --bg-color: #f8f9fa;
 }

In this example, the `.container` class defines a custom property called `–bg-color` with a value of `#ffffff`.

The `.card` class then uses this custom property to set its background color.

However, the `.card-secondary` class overrides the value of `–bg-color` with a new value of `#f8f9fa`, causing the background color of elements with this class to be different from those with just the `.card` class.

Overall, CSS Custom Properties are a powerful tool that can greatly simplify your code and make it easier to maintain.