Comment by ErroneousBosh

It's a different principle, although I have a Ladybird Book of Electronics that my dad gave me when I was just about the age my son is now, that shows how to make a thing that flashes two lightbulbs using that astable circuit (and a few other things).

The two-transistor metronome one really is working more like an SCR, that rapidly charges the capacitor and allows it to discharge again.