Fiddled with delays.

Added timeout to door close, in case sensor isn't reached because of blockage. Increased door open time slightly.

Lowered brightness threshold to 600.

Only supply power to sensors when needed. Added debugging.

Use Narcolepsy library for sleep. Add hysteresis. Lower dark threshold.

Moved pins around so that external button can be used for wakeup. Set up delays and brightness values for first try. Rejigged brightness rolling average calculation.

Initial version, uses photocell and door contact and powers down the Arduino for 8 seconds at a time while waiting.