User interface and user experience design.
User experience design nowadays is mostly human-centred digital spaces navigation, but it's stemming from human-centred design in general. It used to be ergonomics and psychology of colours, shapes and composition perception, — the basis of any purposeful design approach no matter the medium. The examples below display the most common for the modern market notion, — digital interface and structuring of the information behind it. But what is not in this gallery are numerous cases of making things more convenient for people, meeting their needs and improving their experience, whether it's a PDF form or a web-based app interface.
If you see certification as a considerable attribute here are some relevant ones:
Background design, interface elements.