Speaking of physics-based efforts, Phun is a sandbox project:
Phun is meant to be a playground where people can be creative. It can also be used as an educational tool to learn about physics concepts such as restituion and friction.
It’s in beta, but still usable, and has the following features at present:
- Polygons, circles, planes and springs
- A very simple physics engine (temporary)
- A GUI for choosing different tools (brush, plane, circle and spring)
- A console and the Thyme scripting language