Nuclear Weapons

A Nuclear unit (type 25) can be built once anyone has completed the Manhattan Project and its owner knows Nuclear Fission. It is an aircraft with a fuel of one turn and 16 moves. It explodes when it enters a foreign city (the move handler removes it and calls atom(owner, x, y) in BATTLE.C) or attacks a unit (battle() calls atom() on the defender’s tile).

The blast

atom():

1. reports “… use nuclear weapons!” unless the human launched it;
2. plays the explosion (nuke_animation() in DIPLOMAT.C);
3. visits the target tile and its eight neighbours. On each tile with units, all of them (up to ten, see Stacks) are destroyed and counted as losses. This includes the attacker’s own units, so a Nuclear unit attacking from a neighbouring tile destroys itself. A city tile with SDI Defense reports “SDI protects …” and keeps its units;
4. sets 0x088 in treaties[victim][attacker] for each civilization that loses units: a grievance and the nuclear flag. The flag allows later AI nuclear strikes against the attacker;
5. calls nuke_fallout().

nuke_fallout() visits the same nine tiles. Every city loses half its size, rounded down (size -= size / 2). Each land tile without a city is polluted two times in three. SDI Defense does not prevent either effect.

Pollution and global warming

add_pollution() in CITYMGT.C sets map flag 0x40 and increments the global count polluted. Each polluted tile costs ten points of score, and a polluted tile’s yields are halved, rounded up (Tile Yields). Settlers clean a tile in four turns.

Each turn ai_event() in TURN.C moves warm_levels one step towards polluted * 2 - warming * 4. When it reaches 12 with more than six polluted tiles, a news item reports “Scientists alarmed by rising temperatures. Global Warming feared!” Above 16, global_warming(warming++) in WORLDGEN.C changes the climate and the level returns to 0. Each previous warming lowers the target by four, so the next one needs two more polluted tiles.

global_warming(severity) considers every Desert, Plains, Grassland and Forest tile:

• A tile with at least 7 - severity ocean neighbours floods. Forest becomes Jungle and the others Swamp, and irrigation and mines are lost.
• Otherwise, one tile in eight (chosen by (x * 11 + y * 13) & 7 == severity) dries. Desert and Plains become Desert, Grassland and Forest become Plains.

The message reads “Global temperature rises! Icecaps melt. Severe Drought.”