Creative, for kids it also improves counting besides imagination
If the "lentils" slide down and the image is "cleared", two can end up on top of each other and the magnetic pen cannot move the top one. Likewise, when you move a lentil into position and have to drag it over another lentil, the pen often keeps going but the lentil stops against the one underneath. So move the lentils away from existing positions and slowly.