Those involved in interface design are responsible for managing what the user of a site or app sees and making it usable for all the needs of the surfer.
The UI designer designs an interface to allow the user a satisfactory experience and works together with the UX designer to define the relationship the user will have with the final product.
Typography, for example, is a key element in building the appearance of the digital product and is also used as a graphic element: the typeface in its choice, size, color, contributes in an essential way to shape the content.
Website designers should be aware that format, color, contrast, and readability will be different, depending on the device with which the user will access and the tools that will convey the content message.
Cross-browser incompatibilities can make UI work difficult, which is why standards have been established in certain design environments such as Material Design. Material Design is the Android interface that Google applies to its devices, with the goal of providing a common basis for developing sites that are optimal in all their graphical elements. Interactions in responsive design have precise rules, their mandatory input and output direction animations must trigger expected and predictable reactions, or else a usability deficit that can push the user off the page.