Factorio is a game where you build and maintain a factory. You play as an engineer, who has crash landed on an alien planet. The planet is rich in natural resources for you to use. Go ahead and chop down trees, mine out coal, smelt iron and copper, do whatever you can to make the tools and resources you need.
Be wary, the natives don't appreciate your presence and will do what they can to keep their world clean and pollution free. So make sure you're well armed.
You can buy the game direct from the developers here. Make sure you select that you want a Steam version if that's what you want. Or you can get it directly on Steam.
The developers have said repeatedly that they do not believe in sales of software and they will never put Factorio into a Steam sale, so there's no need to delay. If you want to join us, get it. I highly recommend it.