The main objectives of any UI are to facilitate interaction and communicate the state of the game to the player.
Some products can get away with little UI other than game menus and occasional control prompts, while others try to avoid using any text in their interface and operate purely on iconography. The efforts to try and minimize the amount of UI and communicate the state of the game purely with game feedback and UX are applaudable and can result in very elegant designs.
Nevertheless, the more complex your game systems get, the more complex the states they produce. Deep and extensive user interfaces are often unavoidable, and knowing how to design them (or at least how to support and understand the professionals that do ...
