Ideal Gas Simulation, with Maxwell's Demon

This simulation uses Easy Java Simulations (Ejs) to model a two-dimensional ideal gas in a rectangular box, monitored by Maxwell's Demon (which allows only faster than average particles to move from the right side to the left side, while allowing only slower than average particles to move the other way). The particles are initially spread throughout the box with random positions and random velocities (with a Maxwell distribution of speeds). The top view shows an animation of the motion of the particles in the box, while the lower view shows plots of the temperature of the gas on each side of the box (red=left, blue=right) as a function of time. Note that faster than average molecules are shown as green dots, while slower than average molecules are black dots.

Controls:

Play/Pause: starts (or stops) the simulation.
Step: advances the simulation by one time step.
Reset: resets simulations with initial parameter values.
Erase: erases the plot.
Reverse: reverses the velocity of all particles.
N: sets the number of molecules in the gas (up to 500).
Demon On: checkbox to turn Maxwell's Demon on or off. When the box is checked the Demon is On.
Speed (fps): slider to control the speed of the simulation, in terms of the number of frames displayed per second. Higher values make the simulation run faster.

Units are defined so that Boltzmann's constant, the mass of each particle, the length of the box, and the absolute temperature of the whole gas are all equal to one.