SCSS (Sassy Cascading Style Sheets) is a preprocessor for CSS that extends the capabilities of traditional CSS. It is a superset of CSS, meaning that any valid CSS code is also valid SCSS code. SCSS introduces additional features and functionalities to CSS, making it more powerful and flexible for styling web pages. Here are some key features of SCSS: 1. Variables: SCSS allows the use of variables, which can store values such as colors, font sizes, or any other CSS property. Variables make it easier to reuse and maintain consistent styles throughout a project. 

$primary-color: #ff0000;

.button {
  color: $primary-color;
}
2. Nesting: SCSS allows nesting CSS selectors, which provides a more intuitive and organized way of writing styles. Selectors that are nested within other selectors inherit the styles from their parent selectors. 

.container {
  background-color: #f0f0f0;
  
  h1 {
    font-size: 24px;
  }
  
  p {
    color: #333;
  }
}
3. Mixins: Mixins are reusable blocks of code that can be included in multiple selectors or rules. They allow you to define a set of styles and apply them wherever needed, reducing code duplication. 

@mixin flex-center {
  display: flex;
  justify-content: center;
  align-items: center;
}

.container {
  @include flex-center;
}
4. Partials and Imports: SCSS allows you to break your CSS code into multiple files called partials. Partials are prefixed with an underscore, indicating that they are not compiled into separate CSS files. You can then import these partials into a main SCSS file. 

// _buttons.scss
.button {
  // Button styles...
}

// main.scss
@import 'buttons';
5. Operators and Calculations: SCSS supports various mathematical operations, allowing you to perform calculations within CSS properties. This can be useful for dynamically calculating values based on variables or other properties. 

$base-font-size: 16px;

body {
  font-size: $base-font-size * 1.2;
}
To use SCSS in a project, you need to compile it into regular CSS using a preprocessor or a build tool. There are several options available, such as Sass, node-sass, or webpack with sass-loader, that can compile SCSS files into CSS. SCSS simplifies and enhances the process of writing and maintaining CSS stylesheets, making it a popular choice for frontend developers working on complex projects.