This is not so much a bug report or question as it is me just listing some possible extra resources!
This is an example Design Document that I used for my Game Design course in college. It’s an excellent baseline for getting started!
I think Blender also needs an explicit mention, since it’s discussed later in the Resources .pdf, and has excellent tutorials available! Along with it I would recommend Tiled for making 2D grid-based maps (or not grid-based).
For the music-compositionally gifted, I would recommend Finale Notepad or MuseScore for notation and playback (Notepad I believe will only export as MIDI, but there are online services that can convert to mp3).
I would have linked each piece of software, but as I’m new I can only post 2 links. Copying the name and searching it with Google should be fruitful, however.