Reduced sight
From 9 pm to 3 am, units see 2 tiles less; 1 tile at 7 pm and 5 am. Buildings and drones always see just as far: watchtower and surveillance drone are the eyes of the night.
The game starts at 7 am and each turn moves time forward by 2 hours: a day lasts twelve turns. The dial at the top right of the screen shows the time.
From 9 pm to 3 am, units see 2 tiles less; 1 tile at 7 pm and 5 am. Buildings and drones always see just as far: watchtower and surveillance drone are the eyes of the night.
At night, foot troops get tired: a quarter fewer action points, except next to a barracks of their side. They still fire, but do not move as far. Vehicles and helicopters do not tire.
Headlights and lamps come on at nightfall, without changing sight at all: it is atmosphere, not a rule.
Short sight, an enemy who cannot see as far: night favors infiltration and ambush. Units on overwatch remain your best guard.
The season changes every 18 turns. The game starts in summer, then come autumn, winter and spring. Its icon is at the top right, next to the time. Roads, bridges, helicopters and the tow truck ignore mud and snow.

Dry ground: no mud, no snow, no flood. It is the reference season, and the season of forest fires.
A forest can catch fire by itself, only by day, one turn in 6.

Rain: units see 1 tile less. Mud as in spring, but vehicles get stuck one time in six. Marshes, full of water, are closed to all; those already inside can get out. A burning forest goes out twice as fast.

Snow: units see 1 tile less and everyone moves a shorter distance off-road, vehicles even more so. Marshes and rivers freeze: foot troops cross the river, the ice does not carry a vehicle. No forest catches fire and nobody gets stuck any more.

Mud: off-road, everyone moves a shorter distance on grassland, marsh, crater and scorched earth, vehicles even more so. Only vehicles get stuck, one time in eight, twice as often in a marsh; stuck, a vehicle still fires, and a tow truck pulls it free.
Scorched earth grows back into forest, except where the engineers placed a work, a building or a mine.
A mission keeps its own season and time of day: “The Fortified Island” is played on a frozen lake, “Fort Alamo” until dawn…