Okay, the design for Planitia is firming up in my head.
Planitia is going to consist of a series of levels, each one of which is self-contained.
On each level there will be a village of people running as part of a world simulation. But they have a problem, and because of this problem, the population of the village is trending downward – they will soon cease to exist. They do not have the power to save themselves, and thus they have begun to pray for a supernatural entity to aid them. This summons you. Your job is to help them overcome their problems and begin growing instead of dying. Therefore, the way you win a Planitia level is to get your followers to the point where they no longer need you. Then the current level will end and another group of desperate people will call for your aid which will start the next level.
Your one resource is mana. How fast it generates depends on how many believers you have and how fervently they believe in you. If you have no followers your mana will slowly start to drain. If you ever get to the point where you have no mana and no followers (and thus no mana generation) then you cease to exist and have lost the level.
The problems will be different on each level. It could be as simple as “we can’t grow enough crops to feed ourselves any more” to “another group of more advanced villagers has sworn themselves to our destruction”. In any event, it will be up to you to use your tools to aid your people. Yes, there will be combat, but it won’t be on every level.
The things you can do with your mana:
Direct Intervention: Flames, lighting, rain, terrain movement, etc. These will cost a lot of mana, but they will also generate a lot of belief; nothing like seeing a bolt of lightning coming out of the sky to strike down the enemy general to make you believe in your deity.
Civilization upgrades: You can spend mana to divinely inspire one of your villagers. They will then be able to do certain things more effectively. This requires far less mana than direct intervention, but the change will take a while to propagate through the village. The change will be permanent, however.
Direct villager control: You can actually tell your little guys what to do, but it will cost you mana to do so. (Yes, I know this sounds tetchy, but bear with me – as a god, you cannot do anything in the game world without spending mana.) Basically what this means is that all units under your direct control become a mana drain rather than a mana source. Thus, you want to make sure you’ve got at least one unit back home generating mana for every unit in your army that you are directly controlling. I don’t want to make this too punishing; it’s basically going to be there to prevent people from turtling and creating humongous armies. I mean, yeah, you can create that humongous army, but you can’t tell it to go anywhere. I may also make it so that if you are fighting another god, it costs a lot more mana to send units into land that he controls than normal…but that might make the game too defensive. The whole point of this mechanic will be to cause players to strike a balance between offense and defense.
I may make it so that you gain new abilities as you clear lands…but then that has the whole “why not just give me all the toys up front” problem.
So it’s firming up. It’s not too firm yet. It’s cheesecake, not concrete.