Creative Code Libraries
Graphics libraries make it easier to write objects to a canvas or SVG.
They typically give you tools to create, manage, move, and set listeners on items.
Tweening libraries move things from point A to B.
It's called tweening because they handle the action "between" the assigned points.
3D libraries typically give you the ability to make primitives - planes, rectangles, and spheres.
You can design more complicated objects in a modeling program. You're constrained by polygons.
You don't need to be a 3D modeler, you can do a lot of clever things just with primitives.
Physics libs give your objects "real world" heft—gravity, inertia, and collisions.
If you've played Angry Birds, you've seen the basics of a physics engine.
They're also seriously constrained by the number of objects, particularly when you want collisions.
These require another device that the user must own.
Other platforms to explore: