I knew you wouldn't disappoint :)
Since you took this project so serious I will give my feedback:
1. I really like the darkness mechanic, it just took me a while to understand it.
2. The Icons and the general UI is doing the job and the game is very easy to control, no critiques here!
3. Maybe and indication on how long until the next day/turn would be great. On the second version of my city builder I used an Hourglass.
4. I left the game open for a while on late game to farm light and when I came back almost all map was covered by darkness again with no way to farm light properly :P so I was stuck without a Game Over or any indication of Defeat.
Critiques aside, I really like and I think this game is really special :) Congratulations!