For its time, Flash Gordon was state of the art, in terms of special effects. The producers spent more money on this serial than had been spent on any serial before. I especially like the part where the (balsa) rocket ships are taking off and, out the back, comes sparks, which arc downwards, and smoke, which drifts upwards, rather than swooshing all in one direction, as we moderns know the exhaust of rockets is supposed to do. And how about those claymen, who could meld into the walls of a cave such that you could not tell that they were there and then unstick themselves from the solid stone and grab you when you walked by? Scary stuff!! I alsolove it that the "fuel" for the "atom furnace" had to be shoveled into the gaping mouth of the reactor by means of coal shovels. How else?