Here's the "full digital" version.... you can't get much simpler for the full functionality

 

One more suggestion keeping it simple.
Set R4 value for brightness.
Set R2 value for ON delay.
Set R3 value for OFF delay.
View attachment 235411

Because of the high gain of the MOSFET, it will rapidly turn on and off once its gate threshold voltage is reached.

 

Because of the high gain of the MOSFET, it will rapidly turn on and off once its gate threshold voltage is reached.

It worked fine on the bench. The 3.9 volt zener diode slows the turn on time
Edited schematic: Increased the zener voltage to 4.7 volt to compensate for the diode drop and added discharge resistor.