Library and demo apps are mobile or web-based applications that are intended for demonstration or sample purposes. These apps are often used to showcase the capabilities of a particular technology or platform, such as a game engine or programming language. Libraries and demo apps can also be used as a tool for developers to test and debug their code or to experiment with new features and ideas. They can also be used to demonstrate the features and capabilities of a particular software or service. Examples of libraries and demo apps include sample code, SDKs, and game engine demos.