What are the approaches to writing CSS?

Main approaches to writing CSS:

1. Classic (global) CSS — styles are written in one or several files and applied globally to the entire project. It can lead to conflicts and support issues with large amounts of code.

2. Modular CSS (CSS Modules) — styles are isolated by components, classes are automatically localized, preventing naming conflicts.

3. BEM (Block Element Modifier) — a naming methodology for classes to improve readability and reusability. Example: block__element--modifier.

4. CSS-in-JS — styles are written directly in the JavaScript code of components (e.g., styled-components, Emotion). It allows dynamic style changes and utilizing JS capabilities.

5. Preprocessors (Sass, Less) — extend CSS capabilities by adding variables, nesting, mixins, and functions, which improves structure and maintainability of styles.

The choice of approach depends on the project, team, and scalability requirements.