A somewhat different kind of lighthouse
Instead of a normal lighthouse, here's a flare that flashes left and right alternately at night. You can build it as a small viewing platform or tack it to a smooth wall.
Instructions:The circuit, which is connected to a light sensor, works with the help of a small clock that runs continuously.
Only at night do the two pistons descend and transmit the signal to the lanterns.
The distance of the sensor to the pistons determines the time at which the light signal starts to flash.