The requirement for the June 2017 24-hour contest is "nightfall":
https://boardgamegeek.com/thread/1789286/24-hour-contest-june-2017
Tips & Resources for Board Game Designers
The requirement for the June 2017 24-hour contest is "nightfall":
https://boardgamegeek.com/thread/1789286/24-hour-contest-june-2017