Adjust charge using the slider and click on the screen to add an object with that charge. The objects can be dragged when the charge is zero Change the number of vectors by adjusting the detail slider. Tails of vectors whose horizontal or vertical magnitude exceeds 20 are shortened and become red. Press the flag a couple of times. I didn't bother adjusting the charge to be a specific unit, so I just used 4500 for coulomb's constant.
