You choose from thousands of open source packages that add new features and functionality to Atom—or build a package from scratch and publish it for everyone else to use.
Atom comes pre-installed with four UI and eight syntax themes in both dark and light colors. If you can't find what you're looking for, you can also install themes created by the Atom community or create your own.
It's easy to customize and style Atom. You can tweak the look and feel of your UI with CSS/Less and add major features with HTML and JavaScript. Check out the video on setting up Atom.
Atom is a desktop application built with HTML, JavaScript, CSS, and Node.js integration. It runs on Electron, a framework for building cross platform apps using web technologies.