Have you ever wondered why the play button for most music players is still the same right-facing triangle that was on every cassette player and VCR? User interface (UI) designers try to develop icons and controls that are so obvious they endure through the years and across technologies. For example, iPhone apps often feel so familiar because many designers use the UI toolkit from Apple with standard fonts and icons. Unlike user experience (UX) design, which has to do with the flow of a program, UI is all about the look and feel of software and hardware. With colorful photographs and helpful illustrations, readers will make the most of this essential coding topic.