Pocket Physics is a physical construction set for the DS. Like in Crayon Physics, you draw objects which then become physical and interact with each other. It uses 0xtob’s DS port of the Box2D library by Erin Catto.

Changes:

Massive speed optimizations!
Fixed the “explosion” bug
As a side effect of this fix, results are now 100% reproducible
Moved to Box2D 2.0 (Box2D now has official DS support!)
Deleting sketches in the loading dialog
Objects that fall out of the world are no longer simulated
.PP files now have a single root elemnt => XML compliance
An author tag is added to the .PP files
Pins now snap to the center of gravity of shapes
There iss a separate version that doesn not save screenshots for people with saving problems with the SuperCard Lite

http://tobw.net/index.php?cat_id=3&project=Pocket+Physics