My favorite game, and an amazing piece of software. Runs smoothly on my laptop, the one where no other game is playable. The developers know how to optimize!
I love the feel of the game, where you start out only with a pick axe and slowly build your base into a monster. How you build it is entirely up to you, and what you think is interesting. For me it is all about trains, as I love making a train network.
The first time you play you will make a million mistakes, and you might not figure out how something work at once, but it is very rewarding once you do, and even more rewarding when you discover a clever way to do it. Then later you discover an even more clever way, or maybe just a different way that leads to an entire new design. There is so much room for creativity in the game, than it almost never gets old. Once you start looking for it on the internet you will see all kinds of crazy contraptions. I recommend that you try things for your self fist tho, as the discovery is a big part of the experience.
I have played the game for 800 hours, and just started a new base where I am going to try some new ideas!