Unity is a game engine which is a cross or multiplatform game engine developed by Unity technology. It comes with built-in IDE and used for developing video games for desktop platform and mobile device. It is a powerful rendering engine fully integrated with a complete set of intuitive tools and rapid workflows to create interactive 3D and 2D game. It is designed to support single-source authoring with multiple platform targeting to simplify cross-platform work. But in reality, there will always be specific tweaks needed for individual platforms. Unity's common toolset support for all platforms simplifies this process greatly.