I have this problem with colonization of planets. I kind of need it because I need some way for the player to say "I want to be here" and to prevent the player from taking all uninhabited planets at once for free, but... it does not fit the rest of the game and it brings a lot of other problems.

Note: PLANET BEING UNHABITABLE FOR A CERTAIN RACE IS NOT AN ISSUE HERE (ASSUME ALL PLANETS CAN SUPPORT LIFE).

Like, what happens if you conquered an alien planet? In a classic 4X you take it over (so it's basicly a free colonization), which is partially broken mechanic in my game since many aliens can spread effortlessly.

Or, what happens when when an alien abandons a planet (which happens with cyclic aliens that die out each season and go back to hibernate to their homeplanet)?

The thing is, planet ownership can be fickle in my game (abandoning planets, planets that were abandoned rejoining and so on). It's a total mess with a lot of unusual cases :D

Also, what actually means that "planet is colonized" (again, terraformation is not an issue here, the planet already can support life)? I tried to make it "you have at least 1 population of your race" and the act of colonizing is "sending 10k population and building the first city, which costs 1000 credits". But, it's not working very well...

From my point of view the best solution would be simply to remove the colonization concept (but then the player would go and grab all planets in range during the first turn...)

maybe look at it as populations/control, and loyalties/resistance.

So Population would add to a faction/players control over a planet and its resources, but there can be modifications to the control level based on military power and such. Throw in loyalties within a population, so that a given player can work to not just try and rule by force and suppress the existing populations when they try and take over, but they can actually lure them over to their side.

Having a battle fleet in orbit of a peaceful agrarian culture who has no military power might mean that you have no population there, but effective control. If you have no loyalty points within the population, then you could face stiff production penalties if the population has any kind of resistance traits.

This lets you craft different kinds of populations, such as a highly passive species who is happy to work, but really doesn't care WHO they work for. They'll have no loyalty to you, but at the same time offer no resistance to your control. As long as you stay 'in power' then you get the full benefit of them as if they were your own population. But if someone kicks you out, then they will face no penalties from that population, they'll just switch over without a fight.

maybe look at it as populations/control, and loyalties/resistance.

Unfortunatelly it won't work in many cases in my game. The aliens are too weird. Like Hive like insects, their "loyalty" is unquestionable, they will always listen to the queen, besides the player can't even communicate with them and they can't work in factories, etc. It would work with humanoid races only (which is a small subset in my game).

For the purpose of the discussion, let's assume the whole alien population was wiped out (it will be simplier and we will go to the core of the problem). What happens then after you conquered such a planet? Do you need to colonize it? Get it for free? But if for free why it differs from uncolonized/uninhabited planets (which you have to colonize)?

Hmmm... two ideas

1. Your owned planets are a graph, let a new planet only be colonized where a path from your home planet to your target planet with only owned planets exists (explain it as safe trading routes whatever).

This although adds the strategically feature, that you can break supply/colonization chains.

2. You can colonize such a planet immediatly, but it needs to grow into a full member of your empire, lets say 10 turns. During this time only limited actions are possible and you can't expand your system from this planet until it has been activated.

This adds the strategically feature, that some aliens can activate a planet in 5 or even 1 turn, or that you can research better activation strategies etc.

I think you can assume there will be explorers and adventurers even Empire takes no measure to colonize this planet. Planet can be of Empire on paper but harsh nature and alien population can be agressive or at least hindering colonization process. Like when New World discovered, only those had to and explorers went there and they had to deal with harsh nature and Indians there.

In that terms, colonization may either be an expensive process like in Avatar (you stuck in a base) or taming environment in time. What defines this would be how precious this planet is for Empire for strategical reasons.

maybe look at it as populations/control, and loyalties/resistance.

Unfortunatelly it won't work in many cases in my game. The aliens are too weird. Like Hive like insects, their "loyalty" is unquestionable, they will always listen to the queen, besides the player can't even communicate with them and they can't work in factories, etc. It would work with humanoid races only (which is a small subset in my game).

For the purpose of the discussion, let's assume the whole alien population was wiped out (it will be simplier and we will go to the core of the problem). What happens then after you conquered such a planet? Do you need to colonize it? Get it for free? But if for free why it differs from uncolonized/uninhabited planets (which you have to colonize)?

Why wouldn't it work? Your insects are just a side that has a locked loyalty trait, so they will never switch loyalties, and would not be counted towards impacting your factories. (Other than possibly degrading output through 'rebel action'.) You add more factors to the process to address what is needed by character types.

I'll suggest that whatever it is that is the driving force behind production for a race must be present on a planet for it to be considered "owned" by that race. With the assumption that you need a population to run factories on an existing home planet, I say it'd make sense that you'd need to be able to somehow get a population (colonist ship presumably or perhaps in some cases you can integrate the local population to your empire) to the new planet to run the factories there. Military units on or around a planet won't be sufficient to claim a planet but their presence will certainly impact your ability to keep the planet.

Hmmm, probably I will go for "cities". When you perform "colonize" action it builds a city. If you conquer a planet from humanoid aliens you can claim it since it already has a city (of alien design, which is lower quality, but still a city). But if you conquer a planet from insects you don't get it (the planet becomes uninhabited) because insect have "tunnels cities" that do not count as a valid humanoid city.

This would also add a nice dynamic that you don't hesitate to bombard insectoid planets (you prefer to burn everything to the ground) while for civilized races (humanoid) you avoid bombardment since you want to grab the infrastructure (and maybe even population).

Or it might also make sense that you'd need to setup some sort of government building to be able to say that it is indeed part of your empire. It'd be some way to provide communications with the homeworld, issue commands, and distribute resources, It's not hard to say that without some form of government the planet can't really be considered part of an empire. On that thought if there's no form of political agreement or understanding of borders between the player and some opposing race, who "owns" a planet isn't really relevant. If it's not possible to get such an agreement with a race of insects, for example, then both sides just see the other as having no actual right to the planet they're inhabiting.

Government building sounds interesting... Can you expand the idea? Especially, what if you conquer a planet form humanoid aliens? Do they have this government building you can claim?

If this doesn't fit then, what should it actually mean to the player when he "gets" a planet like that. It's kinda sounding like there's some sort of problem you're concerned about if a player were to gain control of a planet and then loose it again. What are the sort of problems that you're facing?

Well, what you wrote fits, I suppose... My problem is that I have separate "owner" flag and I absolutely need it (if nothing else for visuals, need to see "the flag" on the map). And sometimes The player will lose the planet (ownership flag) without losing population and infrastructure, then the alien that took it over will extinct so the planet will become neutral (and can rejoin the empire). Sometimes the population will extince but not the infrastructure, some times it wil be opposite and the population will stay but infrastructure perish. There is a lot of these weird and messy situations in my game :)