Phoenix

Bootstrap is the most popular CSS Framework for developing responsive and mobile-first websites.

Less CSS is a dynamic stylesheet language that extends the capabilities of CSS, allowing developers to write cleaner, more modular, and reusable stylesheets with features like variables, mixins, and nested rules.

ESLint is a linter for JavaScript that analyzes code to detect and report on potential problems and errors, as well as enforce consistent code style and best practices, helping developers to write cleaner, more maintainable code.

Gulp.js is an old but popular site building tool that automates various repetitive development tasks in web development, such as compiling Sass, minifying JavaScript, and optimizing images.