This is a small program I made for the RetroGame 300, though it should work on any compatible hardware as well. It is basically a customizeable music box. You just take some .wav files and name them correctly and then you can play the songs and some sound effects by pressing the buttons on the RetroGame hardware. It currently supports 16 different songs, 4 different sound effects for the ABXY buttons, and a welcome sound.

My infant daughter became very infatuated with my RetroGame 300 and constantly wanted to use it though she was incapable of actually doing anything with it. I made this program as a way of teaching her the basic colors (red, blue, green, yellow), as well as giving her some songs to listen to while mashing buttons. Of course she's gotten quite good at using it, and she sometimes listens to her favorite songs while laying down before a nap or while getting her diaper changed.

Included in the archive below is the program, some dummy wav files to demonstrate the filenaming scheme, the source, and a readme.txt. This is a VERY simple program, so it's very small (14k zipped). Most of the space used by the program will be in the wav files. Please see the readme.txt for more info on installation, source, etc.

I'll go ahead and post the source below in case that's more useful to people looking for examples of code written for OpenDingux:

Additionally, if you're looking for more information about coding for such mobile retro consoles, a good place to start is: https://wiki.dingoonity.org/index.php?title=OpenDingux:About
and:
https://wiki.dingoonity.org/index.php?title=OpenDingux:Development
and a good example with more good links (though not exactly RetroGame300 and different from what I went through):
https://github.com/RG350C/rg350-write