UDK

UDK is a game engine developed by Epic Games. First released in 2007, UDK was designed to be cross-platform, supporting development for the Windows, Mac OS X, and availability of Linux development.

UDK is based on Epic Games' Unreal Engine 3. It isometric and isometrically scalable, meaning it can scale down to much smaller resolutions than most other game engines of its time. This allowed it to be used to develop the browser-based game "Infinity Blade," which became popular for its mobile-friendly design.

One of the key features of UDK is its support for Kismet, a visual scripting language that is used to set up games logic. Kismet can be used by developers, and provides a simpler alternative to writing code in the game engine's programming language.

At one time, UDK was free to use, with only a 5% royalty on gross revenue generated by games sold, which is lower than the typical 10% to 15% royalty rates other engines offer. In 2015, Epic Games announced that it would be shutting down its UDK project, and that Unreal Engine 4 would become the main future engine.

UDK has been widely adopted in the game development industry, and has been used to create a variety of different games. One notable example is the "GTA: Vice City" levels developed for the "PayPay HD" modding community project.