Implementing the app opcodes for basic functions such as saving and loading settings, setting the window, switching from windowed to full screen and so on.

I think I might not even bother to reinvent the wheel and I'll just import the lingo package from the other game we're working on - I wrote it thinking of reusing it later, wrote a nifty little tool to manage all the different strings for a single project, and the GML side of things keeps only the current language in memory, and can even show stuff like missing languages and such.

I made it in Python very shoddily (like everything I write) because it was getting tiresome to manually edit different versions of the same language file and keep them all updated, but it does the job well enough - generates minified .json files with all the corresponding keys for each language and corresponding metadata.

Next thing: menus.

Up until the next time I can say anything! I still have no idea why people do these!