Click and drag to rotate the camera.  
  Control-click and drag to zoom in/out.  
  Right-click and drag to translate the camera.  
     
  Shift-click on a particle to select it, use the arrow keys to move it around.  
     
  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.  
  C: Make all the particles transparent.  
     
  ]: Pause the the simulation  
  I: Show/Hide instructions.  
     
  S: Generate a surface based on the particle positions.  
     
  NOTE: Generating a surface may take a few seconds, depending  
  on the number of particles in the simulation, and CPU speed.