Unity is an all purpose game engine that supports 2D and 3D graphics, drag and drop functionality and scripting through C#.
Unity is particularly popular for mobile game development and much of their focus is on mobile platforms. Unity3D’s 2D pipeline is a more recent addition to the engine, and is less mature than the 3D pipeline. Despite this Unity is an adequate platform for developing 2D games even when compared to other dedicated 2D engines, particularly if you plan to release the game across multiple mobile devices.
Unity is also a good choice for VR development, although VR is a very small market at the moment. The mobile and PSVR markets are the largest in VR, and Unity is already well positioned to port games to many platforms such as PS4 and PC, or many different mobile markets.
The engine targets the following graphics APIs: Direct3D on Windows and Xbox One; OpenGL on Linux, macOS, and Windows; OpenGL ES on Android and iOS; WebGL on the web; and proprietary APIs on the video game consoles.
Additionally, Unity supports the low-level APIs Metal on iOS and macOS and Vulkan on Android, Linux, and Windows, as well as Direct3D 12 on Windows and Xbox One. Within 2D games, Unity allows importation of sprites and an advanced 2D world renderer.
For 3D games, Unity allows specification of texture compression and resolution settings for each platform that the game engine supports, and provides support for bump mapping, reflection mapping, parallax mapping, screen space ambient occlusion (SSAO), dynamic shadows using shadow maps, render-to-texture and full-screen post-processing effects.
Unity also offers services to developers, these are: Unity Ads, Unity Analytics, Unity Certification, Unity Cloud Build, Unity Everyplay, Unity IAP, Unity Multiplayer, Unity Performance Reporting and Unity Collaborate. Besides this, Unity has an asset store where the developer community can download and upload both commercial and free third party resources such as textures, models, plugins, editor extensions and even entire game examples.
Unity is notable for its ability to target games for multiple platforms. The currently supported platforms are Android, Android TV, Facebook Gameroom, Fire OS, Gear VR, Google Cardboard, Google Daydream, HTC Vive, iOS, Linux, macOS, Microsoft HoloLens, Nintendo 3DS family, Nintendo Switch, Oculus Rift, PlayStation 4, PlayStation Vita, PlayStation VR, Samsung Smart TV, Tizen, tvOS, WebGL, Wii U, Windows, Windows Phone, Windows Store, and Xbox One.