Libretro is a simple but powerful development interface that allows for
the easy creation of emulators, games and multimedia applications that
can plug straight into any libretro-compatible frontend. This development
interface is open to others so that they can run these pluggable emulator
and game cores also in their own programs or devices.

Citra is a work-in-progress Nintendo 3DS emulator started in early
2014. Citra can currently emulate, with varying degrees of success,
a wide variety of different homebrew applications and commercial software.