There are thirteen lighted lamps arranged in a circle.
You may toggle any set of three on and off
by clicking or tapping on the centre lamp of the three.
Your aim is to turn them all off in no more than twenty moves.
It’s a simple puzzle but the solution is given below in case
you give up. The lamps may be numbered 1 to 13 going
clockwise starting at the top.
Answer Click or tap every lamp once.
The order doesn’t matter and I’m guessing
there are !12/2 or 239,500,800 different variations
ignoring rotation and reflection. You are allowed to
groan having discovered that the answer is so simple.
Javascript mechanism courtesy of Phil Filippak