Very clever. Made possible by the energy efficiency of LEDs.
One thing though, in the opening the narrator says "...doesn't require any kind of energy." That is wrong of course. Where the energy comes in is that someone must lift the rock (weight). Granted it's human/muscle energy, but energy none-the-less. Gravity isn't an energy, btw, but a force that creates energy.
Still a great use of low current LEDs, small generator and high gear ratio gravity motor. Not unlike old grandfather clocks.