Freeciv

It's a while since I last looked that part of the code, but I think you can have requirements like ("Terrain", "Forest", FALSE) and ("Terrain", "Jungle", FALSE) for the pollution extra if you want.

Yes, "NoPollution" is just a user flag now. You can make it so you can have Fallout but not Pollution on these terrains.

Ah, ok, I didn't know. Then I have a question about pollution, to know if it is worth to keep this rule.

When the game engine decides that a city has produced 1 pollution this turn, then (1) it chooses one tile where pollution is possible to place it. Or (2) it randomly chooses a tile, and if pollution is not possible in this tile, then the pollution is not generated.

When I introduced this rule I liked the idea to encourage players to keep some forests/jungles around their cities to reduce the effect of pollution (eco-friendly, you know), but in case of first answer (pollution is generated anyway in another tile), then it is not so good to keep forests around cities, because it forces pollution to appear in other better tiles.

If the answer is (2), then I'll make another patch. If the answer is (1), then I vote to use the current patch.

The answer is effectively (1). cityturn.c:check_pollution looks 100 times for a random tile on which it can place a new pollution extra, making it very likely that if there is such a tile/extra, it will be found.

If the answer is (1), then I vote to use the current patch.

OK.