Charges may be placed in either or both of the two adjoining dielectric half-planes

Use the sliders or entries in the display panel, to set the permittivities of the
two dielectrics

Use the slider or the entry, in the Input panel, to set a positive or negative value
for a new charge to place in the display panel

Use "add charge" and click in the display panel to put charge there

Select a charge and click "edit charge value" to see the effects of the change

Selected charges may also be deleted or dragged to a new location in the display panel

Electric potential V(x,y) is shown in shades of blue (positive) and red (negative)

Contour lines of constant potential are displayed in black

Electric field vector directions are shown as dark blue arrows

The cursor can also be used to echo the Potential and Electric Field values
at that position