An effect stolen from the old days - updated now that we have this new-fangled floating point stuff, and larger integers
A one-liner that dips in just under the 25 command limit:
Rate# = 0.1 : sync on : sync rate 0 : sync : sync : Level as double integer : Width = screen width() / 2 : Height = screen height() / 2 : for Zoom# = -30.0 to 30.0 step Rate# : lock pixels : for x = 0 to Width - 1 : for y = 0 to Height - 1 : Level = (x * x) + (y * y) : Level = (Level * Level) / (2.0 ^ Zoom#) : dot Width + x, Height + y, rgb( Level, 0, 0 ) : dot Width - x, Height + y, rgb( Level, 0, 0 ) : dot Width + x, Height - y, rgb( Level, 0, 0 ) : dot Width - x, Height - y, rgb( Level, 0, 0 ) : next : next : unlock pixels : sync : next Zoom#
If it runs a little too slowly for you, just change the Rate# variable to a slightly bigger number. It runs in a little over 18 seconds on my machine.