Introduction

In this tutorial, we will delve into the basics of defining and using CSS variables. CSS variables, also known as CSS custom properties, let you store specific values for reuse in your style sheet. This can significantly simplify your code, making it more readable and maintainable.

By the end of this tutorial, you will be able to declare CSS variables and apply them within your styles.

Prerequisites

To get the most out of this tutorial, you should have a basic understanding of HTML and CSS. Familiarity with writing and applying CSS styles is particularly important.

Step-by-Step Guide

CSS variables are declared within CSS selectors. They are defined with a double dash -- and are case sensitive.

Syntax for declaring CSS variables

:root {
  --main-color: #c06;
}

In the above example, --main-color is a variable set to the color #c06. The :root pseudo-class selector is used to ensure the variable is available globally to the entire document.

Syntax for using CSS variables

element {
  property: var(--variable-name);
}

Here's an example of how to use the --main-color variable:

body {
  background-color: var(--main-color);
}

Code Examples

Let's look at some practical examples of using CSS variables.

Example 1: Changing the color scheme of a webpage

:root {
  --main-bg-color: #f0f0f0;
  --main-txt-color: #333;
}

body {
  background-color: var(--main-bg-color);
  color: var(--main-txt-color);
}

Here, we've defined two variables, --main-bg-color for the background color, and --main-txt-color for the text color. We then apply these variables to the body element.

Example 2: Using CSS variables in calculations

CSS variables can also be used in calculations, as shown in the following example:

:root {
  --base-font-size: 16px;
}

p {
  font-size: calc(var(--base-font-size) * 1.2);
}

In the above example, we've defined --base-font-size as 16px. We then use this variable in a calculation to set the font size of paragraph elements to 20% larger than the base font size.

Summary

In this tutorial, you learned how to declare and use CSS variables to make your stylesheets more maintainable and flexible. CSS variables are a powerful tool for managing your site's design, particularly for larger projects or for themes that need to be dynamically changed.

The next steps in learning more about CSS variables include experimenting with them in your own projects and reading the official documentation.

Practice Exercises

1. Exercise 1: Declare a CSS variable for a border color, and use it to style the border of a div element.

2. Exercise 2: Declare two CSS variables for a base font size and line height. Use these variables to style a paragraph of text.

3. Exercise 3: Experiment with changing the values of your CSS variables and observe the result.

Solutions

1. Solution 1:
   ```css
   :root {
   --border-color: #ccc;
   }

   div {
   border: 1px solid var(--border-color);
   }
   `` Here, we declare the variable--border-colorand use it to style the border color of adiv`.

2. Solution 2:
   ```css
   :root {
   --base-font-size: 16px;
   --line-height: 1.5;
   }

   p {
   font-size: var(--base-font-size);
   line-height: var(--line-height);
   }
   `` In this example, we declare the variables--base-font-sizeand--line-height`, and use them to style a paragraph of text.

3. Solution 3: This exercise is subjective and is left for the learner's experimentation.

For further practice, try to use CSS variables in your next project. It will give you a better understanding of their potential and usage. Happy coding!