FreeChaF is a Fairchild Channel F emulator implemented as a libretro core. It was designed for use with RetroPie on a Raspberry Pi 3. The primary goal was to allow my wife and I to play the built-in pong variant together easily.
A "console mode" overlay allows players to easy play on a typical SNES or PlayStation style joypad. The console buttons and a description of the selected button is shown on-screen by pressing the retropad "start" button.
On controllers with dual analog sticks, the controls are duplicated. The left analog control allows forward, backward, left, and right movement just like the joypad. The right analog control maps up to "pull up", down to "push down" and left and right to "twist left" and "twist right" respectively.
The select button lets you switch the left and right controllers. Some games expect the left controller to be player one, others expect the right controller. This isn't a problem if you have two controllers (and don't mind juggling them) but users with only one controller or using a portable setup would be effectively locked out of some games. Pressing select from either controller with swap the left controller for the right and vice-versa.
I'll post more about it sometime in the future. For now, you can download it here:
Link 1: SourceForge Update: It's on GitHub now: https://github.com/libretro/FreeChaF The libretro ‘buildbot’ should soon start producing pre-compiled binaries for other platforms.