For the current AppGameKit app jam on itch.io I've created a tool that lets you play with 2D particles, sin/cos orbits, and sine waves. You can play around with each in real time by adjusting a number of different settings. Once you're happy with what you've produced on screen you can copy and paste the code into your own AppGameKit app or game.
I plan to add more to it after the jam, as there was lots I couldn't get added in time.
If there's anything you'd like to see in a future app, or if you find problems with it please report them via the channels provided within the application (see the about screen)