This describes one of the most pleasing hacks I've ever come across. I just now tracked it down and added it to my bookmarks. (Not sure why it wasn't already there.)

You could also conceive of going one step further. When your app (doesn't actually have to be a game, though admittedly it's much easier for you if it is) is compiled with tweak.h, it gives it the power to paint the source file on the screen—so you don't actually have to switch over to your text editor to save it, etc. Suppose you want to provide custom inputs like Bret Victor-style sliders for numeric values. You could edit it in your text editor, or you could derp around with it in-app. Tweaking the value in-app should of course both update it wrt the app runtime but also still write the file to disk, too, so if live reloading is turned on in your text editor, whatever changes you make inside the live process image gets synced out.