Open Simulator with Physics Engine

[Yoshiki Ohshima]

  It is not something done with a physics engine, but there are a few
particle systems written in Etoys.  For example, if you launch Etoys,
click on "Gallery of Projects", and click on the thumbnail third from
the left in the bottom row.

  It is an ideal gas simulation (in 2D).  You can modify the
parameters like pressure (called "gravity" because the green top wall
is falling down all the time), and turtleCount that controls the
number of gas molecules.  But also you can modify the actual
simulation code while the simulation is running, change stuff in the
script called "oneStep", or perhaps you can assign different values to
the "speed" variables to these molecules' own variables, etc., etc.

-- Yoshiki