A tiny board that you can tape to any object and that gives you a nice faint cool white light when it gets dark, trying to resemble moonshine.
It runs for a few weeks on a CR2032 battery.

You can adjust the brightness threshold for when to turn the lights on with a potentiometer. The voltage comparison is made with a small low power op-amp.

I got the idea to do this project from turning off my kitchen lights which are LED based and have this nice effect of tinting the whole room in a faint white light that looks like the moon is shining "brightly" into the room for a second, so I wanted to re-create that effect with low power LEDs.

I put a bit of thermo plastic around the LEDs to increase the diffusion of the light.
The light dependent resistor should face away from the LED as much as possible.