So how fun is this game, going in blind?

[C-zom]

I just saw it's on a nice sale and I happen to have $16 in my steam wallet, and I've had it for months. Nothing but ONI has caught my eye so far. I like Rimworld, Judgment, Factorio, Terraria, etc. Which all are used as adjectives to describe this game. However the management of gas and fluid systems and physics seems a little obtuse to me, those aren't my strong suits and I tend to avoid any of the complicated mods like hygiene for Rimworld for that very reason.

However, is it fun? What can you do with your colonists? Is there a meta game? Combat? Invasions? Economy? Trading? Anything? Say you're about 10 hours into your colony at this moment ,what are you doing to have fun or is it more just upgrading tiers and min/maxing your oxygen and fluids?

[SKull]

The colonists are sims, so you have no direct way of controlling them. Instead you have priorities and jobs that you can assign to the various people. None of the other things you mentioned so far though, although it might change. There is a lot of exploration, but not really any end game. You simply need different resources as you unlock technology which you will generally find as you progress in your exploration. There are also presumed alien ruins, but thus far no aliens to go with the ruins.
For now it is all about surviving; getting enough oxygen, food and electricity produced and then managing heat, disease and other things. But it's a lot of fun if you like sims, base builders or survival games, as it is a bit of a mix of all those three things.

The colonists do have a combat rating still. Although I am less and less sure why, as even critters that were previously hostile on occasion have been turned into pacifists. The game still isn't finished, so things are definitely subject to change.
There are quite complex game elements here that can be made even more complex if you should so desire. But the nice thing is that you don't really need all of it to get far. You might not manage to make your base permanent without complex stuff, but you can easily get it to go for long enough to grow boed by it and start a new one. Things like plumbing, ventilation and electricity are a doddle to build and manage after a little practice though. But you will need to build those.

[MrOrange]

Its very fun and challenging

[SamuraiJones]

This game isn't a cookie cutter city builder. It's survival, not a 4x, so you don't have trading or invasions, but keeping a stable base is challenging. I wouldn't call it overly hard, but it certainly doesn't pull any punches.

10 hours in, you'll have a boatload of problems you're still trying to solve for your colonists. Probably looking for alternative water sources, but maybe starting to having cooling problems.

Tracing plumbing and ventilation paths are a significant part of this game. I can understand how that doesn't sound exciting, but keep in mind most of factorio is laying out conveyor belt paths. Infrastructure in this game is way more complex than rimworld or judgment, but less complex than factorio.

As for fun... I've been told (repeatedly) that I have an obscure definition of "fun" (probably from all my dwarf fortress days), so I won't attempt to answer that one.