In this preset the Ising spins lie in the plane of the array, with allowed orientations up and down in the plane of the screen (the "vertical" choice of the "easy axis"). Now the dipolar interaction is positive at spins located vertically with respect to one another and negative for those to the left or right of one another.
This preset simulates the behavior of a three dimensional ferromagnet which forms a domain structure of slabs of oppositely oriented spins. Think of the screen as a cross section with lines of all up, or all down, spins running perpendicular to the screen. The alignment of the whole line is indicated by the red or white square in the display.
Run to see the formation of the ferromagnetic state, but now with a domain pattern driven not by random nucleation of different domains, but by an attempt to minimize the dipolar energy. Note the typical width of the domains. Now change the dipole D to D = 5, hit the init. button, and explain why the domain structure which forms is finer grained than with D = 0.5.
Change the parameters to J = D = 1 and move the external field slider with the mouse to see the development of a net magnetization via the changes in relative sizes of the two types of domains.