This is from Electronic Playground experiment #26 - The Lighthouse. This is the best I can come up with for the design.
It seems the center-tapped transformer doesn't work as a mutually coupled coil on the primary side in this simulator, so i used a standard transformer and connected the primary to the secondary and use it in a center tapped fashion.
The 1MΩ resistor has been changed to a 1kΩ resistor so it cycles faster.
