Control-click and drag to zoom in/out.
	Right-click and drag to translate the camera.
	Click on a particle to select it, drag to move it around.
	O: Add a neutral particle.
	P: Add a particle of charge +2.
	N: Add a particle of charge -2.
	D: Add a dipole (+2/-2 pair).
	+: Increase the charge on the selected particle.
	-: Decrease the charge on the selected particle.
	X: Delete the selected particle.
	]: Pause the the simulation.
	I: Show/Hide instructions.