Evolution detail of brightening events. Panels (a1)–(a8) present the brightening process of Case-3; the event brightens at a footpoint, and the brightening front propagates along the loop over a finite distance. Panels (b1)–(b8) show the brightening process of Case-6; the event also brightens from the footpoint. As is indicated by the green arrows, small, moving, brightening points are observed near the footpoint, which may provide evidence of reconnection between shorter and longer loops.