I am now working on a new theme for this site, using the Tailwind CSS framework. Tailwind CSS is classified as a utility-first CSS framework which is very low level, meaning you have to create all the components (buttons, headings, alerts, modal windows, cards etc) yourself rather than those provided by a framework like Bootstrap. It is quick to design with, as you use utility classes on your HTML elements to style your site. Responsive design is possible, so you can design for mobile and desktop through the use of prefixes, e.g. <img class='w-16 md:w-32 lg:w-48' src='...'> increases an images width depending on the screen resolution. You can also use pseudo-class variants to style on hover and focus, e.g. <button class='hover:bg-gray-400'>.