1. Introduction

1.1 Brief Explanation of the Tutorial's Goal

This tutorial aims to teach you about nesting pseudo-classes and pseudo-elements in SASS/SCSS. By the end of it, you will understand how to use these special selectors to organize your stylesheets more efficiently and make them easier to read and maintain.

1.2 What the User Will Learn

You will learn about:
- Pseudo-classes and pseudo-elements
- Nesting in SASS/SCSS
- How to nest pseudo-classes and pseudo-elements

1.3 Prerequisites

To get the most from this tutorial, you should have a basic understanding of:
- HTML & CSS
- SASS/SCSS syntax

2. Step-by-Step Guide

2.1 Pseudo-Classes and Pseudo-Elements

Pseudo-classes are special keywords added to selectors that specify a special state of the selected elements. For example, :hover can be used to change a button's color when the user's pointer hovers over it.

Pseudo-elements, on the other hand, allow you to style specific parts of an element. For example, ::before and ::after are used to insert content before or after the content of an element.

2.2 Nesting in SASS/SCSS

Nesting is a powerful feature in SASS/SCSS that allows you to nest your CSS selectors in a way that follows the same visual hierarchy of your HTML. Be mindful not to over-nest, as it can lead to more specificity and code that's harder to maintain.

2.3 How to Nest Pseudo-Classes and Pseudo-Elements

When nesting pseudo-classes or pseudo-elements, you place them within the block of code for the element you're styling. You start with an & symbol, followed by a colon :, and then the pseudo-class or pseudo-element name.

3. Code Examples

Example 1: Nesting Pseudo-Classes

// SCSS Code
a {
  color: blue;

  &:hover {
    color: red;
  }
}

In this example, the &:hover selector inside the a block is equivalent to a:hover in CSS. This means that the color of the link will change to red when you hover over it.

Example 2: Nesting Pseudo-Elements

// SCSS Code
div {
  color: black;

  &::after {
    content: "";
    display: block;
    height: 2px;
    background: black;
  }
}

Here, &::after inside the div block is equivalent to div::after in CSS. This will add a black line after any div element.

4. Summary

In this tutorial, we covered:
- Pseudo-classes and pseudo-elements in SASS/SCSS
- How to nest pseudo-classes and pseudo-elements
- The importance of nesting for maintaining clean and organized stylesheets

Next steps include practicing these concepts with your own projects and exploring other advanced features of SASS/SCSS.

5. Practice Exercises

Exercise 1:

Create a button element that changes its background color when hovered over and shows a tooltip when focused.

Exercise 2:

Make an h1 tag that changes its text color on hover and adds a line before the text on focus.

Exercise 3:

Create an input field that changes its border color when it's active and shows an error message after the field when it's not valid.

Remember, practice is key to mastering any new concept. Use the techniques you learned here in your own projects and see the power of SASS/SCSS nesting firsthand.