if it becomes day or night or if a daybound permanent enters the battlefield, track day/night for the rest of the game.
as it becomes day, transform all nightbound permanents.
if a player casts no spells during their own turn, it becomes night next turn.
//
night
as it becomes night, transform all daybound permanents.
permanents enter the battlefield nightbound.
if a player casts at least two spells during their own turn, it becomes day next turn.
