However, games for a modern PC operating system such as Microsoft Windows must operate within the constraints of the process scheduler. Some modern games run multiple threads so that, for example, the computation of character AI can be decoupled from the generation of smooth motion within the game. This has the disadvantage of (slightly) increased overhead, but the game may run more smoothly and efficiently on hyper-threading or multicore processors and on multiprocessor platforms. With the computer industry's focus on CPUs with more cores that can execute more threads, this is becoming increasingly important. Consoles like the Xbox 360 and PlayStation 3 already have more than one core per processor, and execute more than one thread per core. The only platforms widely available for hobbyists to program are consumer operating systems, such as Android, iOS, Windows, Mac, Linux, etc. This is because development on game consoles requires special development systems that cost thousands of dollars. Often these must be obtained from the console manufacturer and are only sold or leased to professional game development studios. However, Microsoft used to distribute a game development framework, XNA, which runs on both Microsoft Windows and Xbox 360. XNA was discontinued, but other projects like MonoGame and SharpDX are trying to allow the same access for game coding. Lately, Android is the most popular hobbyist platform of choice for mobile developers. Some hobbyists also develop homebrew games, especially for handheld systems or modded consoles. Some software engineering students program games as exercises for learning a programming language or operating system. Some hobbyists may use software packages that help with game development, such as Adobe Flash, Unity, Android Studio, pygame, Adventure Game Studio, GameMaker Studio, Godot, Unreal Engine, or Construct.