Drupal8 W3CSS Theme is using the W3.CSS framework with built-in responsiveness: Smaller and faster than other CSS frameworks. - Easier to learn, and easier to use than other CSS frameworks. - Uses standard CSS only (No jQuery or JavaScript library). - Speeds up and simplifies web development. - Supports modern responsive design (mobile first) by default. - Provides CSS equality for all browsers. Chrome, Firefox, IE, Safari, and more. - Provides CSS equality for all devices. PC, laptop, tablet, and mobile. - Learn more about W3.CSS https://www.w3schools.com/w3css/