> Game engines are, first and foremost, designed to provide a 2D or 3D graphics environment and input handling, they don't typically have the richness of UI com

> Game engines are, first and foremost, designed to provide a 2D or 3D graphics environment and input handling, they don't typically have the richness of UI components that you would expect for building a desktop app. Games are full desktop applications, ad often have full-featured GUIs overlaid on top of a 3D-rendered playfield. Certain game genres, especially strategy games and RPGs, regularly implement full UI toolkits, with floating windows, list and table widgets, combo-boxes, toolbars and menu bars, etc. Some games have a superset of standard desktop widgets in order to account for standard UI functionality along with very game-specific needs. Look at Paradox's grand strategy games for some examples of this. Some people refer to them as "spreadsheet games" because of the complexity of game data and statistics exposed through application-like UI controls.