Xgas, animated simulation of an ideal gas

Xgas is a physical simulation of an ideal gas in a heated box.
Gas molecules move around the box with velocities dependent on
their temperature. A chamber consisting of two boxes contains
the gas molecules collide with the walls, their temperature
approaches that of the box.

Use  mouse  button  1 to create molecules one at a time at
the cursor position.  Use mouse button  2  to  create  the
maximum number of molecules at the cursor position.

Usage: xgas [ -options ]

Options:
      -as   Sets the autoStart resource.
      -ts   Sets the timeStepSize resource.
      -d    Sets the delay resource.
      -rb   Sets the randomBounce resource.
      -eq   Sets the equilibrium resource.
      -mm   Sets the maxMolecules resource.
      -fg   Sets the foreground.
      -bg   Sets the background.