I did a bit of work with the sleep modes but didn't have much luck. Specifically, I had trouble getting interrupts to work during sleep.

In the meantime, I've added a rotary encoder instead of up/down buttons, just because I think as an interface for ordinary people a knob is pretty easy to know what to do. 

I also hooked up photo transistor and NeoPixel stick to use as a nightlight. 

I'm still waiting on an enclosure.