CSS preprocessors are powerful tools that extend the capabilities of CSS by allowing developers to write code in a more efficient and maintainable way. They introduce features such as variables, nesting, mixins, and functions, which are not available in standard CSS. This module will cover the basics of CSS preprocessors, focusing on two of the most popular ones: Sass and Less.

A CSS preprocessor is a scripting language that extends CSS and compiles it into regular CSS. It allows developers to write CSS in a more dynamic and reusable way. The main benefits of using a CSS preprocessor include:

• Variables: Store values that can be reused throughout the stylesheet.
• Nesting: Nest CSS selectors in a way that follows the same visual hierarchy of the HTML.
• Mixins: Create reusable chunks of code that can be included in other selectors.
• Functions and Operations: Perform calculations and manipulate values directly within the CSS.

Sass is one of the most widely used CSS preprocessors. It offers two syntaxes:

• SCSS (Sassy CSS): Uses a syntax similar to CSS, making it easier for beginners to learn.
• Sass (Indented Syntax): Uses indentation instead of braces and semicolons.

Less is another popular CSS preprocessor that is known for its simplicity and ease of use. It uses a syntax similar to CSS and is often used in conjunction with JavaScript.

CSS preprocessors work by taking the preprocessor code and compiling it into standard CSS that browsers can understand. This process involves:

1. Writing Preprocessor Code: Developers write styles using the preprocessor's syntax and features.
2. Compiling: The preprocessor compiles the code into regular CSS.
3. Using Compiled CSS: The compiled CSS is linked to the HTML file, just like any other CSS file.

Let's look at a simple example of using variables in Sass:

In this example, we define variables for colors and font stack, which are then used throughout the stylesheet. This makes it easy to update the values in one place without having to change them in multiple locations.

1. Objective: Create a simple stylesheet using Sass variables and nesting.
2. Instructions:
   • Define variables for primary and secondary colors.
   • Use nesting to style a navigation menu.
   • Compile the Sass code to CSS.

• Variables: $primary-color and $secondary-color are defined and used for the navigation background and hover effects.
• Nesting: The nav element contains nested styles for ul, li, and a elements, making the code more readable and maintainable.

CSS preprocessors like Sass and Less provide powerful features that make writing and maintaining CSS easier and more efficient. By using variables, nesting, mixins, and functions, developers can create more dynamic and reusable stylesheets. In the next module, we will dive deeper into the basics of Sass and explore its features in more detail.