This library works by drawing circles on an HTML canvas element. The base unit for this engine is a pixel, e.g. velocity is in px/s. I put together this little physics sandbox so you can get a good idea of what the library is capable of. Have fun!
Gravity: 0.0
Drag: 0.0
Collisions: ON
Color:
Radius: 75
X-Velocity: 0
Y-Velocity: 0