This was an exercise in complexity for me.  There are 256 neon lamps mounted in a 16 X 16 array on a circuit board that I designed.  The circuitry causes groups of about 8 lamps to flash in widely dispersed groups about 2 times per second.

Each lamp is surrounded by a circuit called a "neon relaxation oscillator".  The circuit consists of a diode, resistor, capacitors and the lamp itself.  The components are connected to 120VAC in such a way that the capacitors build up an DC electrical charge over time to a level that causes an arc across the electrodes inside the neon lamp that is seen as a brief flash of orange light.  The capacitors are wired in a network so that the discharge of one lamp depletes the stored power in it's region.