I have a confession. I don't entirely understand Kerbal Space Program's career mode. You're supposed to perform various experiments to earn money, prestige, and scientific knowledge, but it's not always clear what you're supposed to do. I've been trying to test a parachute for two hours now, but I can't quite get in the altitude window.
On the other hand, iterating rocket designs, tweaking them by adding or removing a part at a time, is a pretty satisfying activity. It's fun to see the subtle differences in power, stability, and maneuverability between slightly different rockets. I could get lost for hours in these tiny details. I know because I almost did.
I'm going to give career mode a little more time to win me over. I like the progression in available parts - it gives me a clear hierarchy of goals to pursue, but I don't like killing my Kerbals on untested spacecraft or running out of money while testing new rocket designs. The missions I could take or leave. They bring structure, but I'm more than capable of setting my own agenda. Science mode might be more my speed (it's like career mode, but without the budgets or reputation mechanics), as it will still allow the technology ramp. Yet, I like having all the doo-dads enabled. There's something about sim games that gives me an insatiable appetite for more detail (it's the same reason I own most of the major DLCs for The Sims 2, 3, and 4). I think it's the fantasy of disappearing into a virtual world.
And Kerbal Space Program has one of the more distinct and fascinating virtual worlds I've ever played. There's not a lot of variety in it - I'm sure the planets of the Kerbal system all have their own unique environments, but I've yet to see much variation at anything less than the continental scale - and yet, there's nothing else like it. It's precisely because things like the continental scale matter. You're controlling a single-occupancy vehicle, but you travel hundreds of thousands of miles at incredible speeds. And that's just a tiny fraction of what's possible.
Most games give up when confronted by the enormity of space. In Space Engineers, the moon was only 140km from the Earth. In any number of space strategy games, planetary systems are more like classroom charts than realistically proportioned. And I'm sure that Kerbal Space Program probably underselling the size of the real solar system (so I googled it and yes, the Kerbal star system is about 1/10th the size of our own), but it at least makes an attempt to come close. It also includes other basic laws of physics that are conspicuously absent from other space games (inertia, being able to accelerate as long as you have fuel, the long range of gravity, etc).
It is this unflinching depiction of the universe as a vast, mostly empty place governed by scarcely-comprehensible energies that sets Kerbal Space Program apart from just about ever other game out there. It may be a lot more barren than something like No Man's Sky, but its emptiness has grandeur all its own.
I don't know how deep into the universe I'm going to get in the next ten hours, but I suspect that there is still a lot out in space with the capacity to surprise me.