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[Schocker]

It is located in ~/Library

Ha, didn't know it's there

Neither did I! I actually had to look through all possible locations and finally reminded myself about the ~/Library directory.

This should be auto-detected to your system language

It might be, but my OS is in English, while I want the game in Polish (for the kids).

What is more, the auto-detect on my MacBook (OS X in Polish) mixes up English and Polish. http://screencast.com/t/OxITv62p
UI elements are in Polish, SatCom and all descriptions are in English. Happened to me as well on Windows when installing the game on school's computer. Maybe I should report an issue on that...

no official option in the menu to change it

That would be cool, I've tried google'ing it, look in the manual and finally found that as a console command. Which is bad for people have who never touched terminal in their lives ;-)

That option is a must. And I think we could benefit from some kind of FAQ or readme for end users or .ini documention or... something like that. Someone who downloads the game for the first time can only wonder how to change the language (I have always changed the language using the parameter) or where are the saves located. We used to have the FAQ page on wiki, but we've abandoned that project, IIRC.