Factorio 1.0 has finally dropped after being in development for 8½ years.
There is a
wiki to help you play this complex thing
There is a
demo to help you decide if you like it before you buy
Here is the 1.0 launch trailer
It's neither open source nor free.
It is DRM free and very easy to pirate. But then you don't get mods or multiplayer.
Right now it is $30 (in whatever your local currency is). It never goes on sale, and only goes up in price as the game improves.
Everything has been meticulously built by professionals. Sprites, animations, sounds, gameplay, language (21 supported languages!) and it shows.
You can adjust everything in the game to make it however you want. Personally I turn off aliens.
There is an overarching goal but the ultimate win condition is your own satisfaction. And if that's not enough, you can mod it with Lua.
You will either love it or hate it.
I love it.