Although I keep changing my mind about how much I personally like the Dyson Sphere Program, there is one thing I can say without hesitation: this is an impressive job. Despite being new to early access, it already has an extremely broad set of features and the kind of extremely ambitious premise that you would dismiss as an impossible dream if it had not yet been implemented.
That premise? To create an interstellar industrial empire, on a scale where you can capture whole stars and put them to work, like those poor dinosaurs that Flintstones would imprison in their appliances. But large galactic oaks grow from small acorns, and this absurd work begins with a single mech, walking on a spherical 3D planet.