Pre-eruptive magnetic field configuration, evolving post-flare loops and moving photospheric currents, as viewed from above. Upper-right panel: cyan/pink contours and greyscale image of negative/positive magnetic fields B_z(z = 0), with the color scale on the right. The yellow line is the PIL. This magnetic field is fixed in time, so the same contours are reproduced in all panels. Upper-left panel: the pre-eruptive magnetic field configuration. The blue (resp. green) lines are typical sigmoidal and highly sheared (resp. large-scale and nearly potential) arcades. The pink lines show the dipped portions of every concave-up field lines. The greyscale image shows the negative/positive photospheric currents . The same is plotted in the lower panels, with the color scale on their right. Lower panels: three sets of post-flare red field lines, each drawn at three different times.