I think the list of gameplay changes is here
I think this is a good list.
Re agents how would they be limited? Would it be with a cooldown (like you can only fire once every 3 seconds) or would it be that they use up ammonia and glucose or something else?
Re O2 and CO2 I agree removing them is a good idea. What would it mean if they were features of the environment? How would that change things?
Same question for pressure, salinity, acidity and temperature, are they just numbers for each patch and if so does it make any difference to the player? I think any feature is much more powerful if it’s rooted in the gameplay.
A few suggestions: I like the idea of sunspots a lot which are the only places where chloroplasts work, especially if all cells can move. I wonder also if we could have lava spots in the vent biome which are orange patches which damage you when you touch them.
I liked the idea of icing happening, not sure how that would work. Maybe ice spots which make you slow and damage you unless you have anti-freeze protein?
Re O2 one option would be to have “the great oxygenation event” which happens after some number of generations, maybe 5, which is just a message you get that unlocks mitochondria in the editor. It would then be quite a game changing moment and would be a big upgrade to the types of cell you could make. For example maybe if you rely on cytoplasm to produce power before this then you can’t make enough power to support a nucleus, however once the GOE happens you can use mitochondria and then you can have a nucleus. That way it’s very tied into gameplay and will be memorable and powerful.
For example:
if cytoplasm makes 5 atp/s, a flagella costs 25 atp/s and a nucleus costs 50 atp/s under your cpu style atp scheme.
then at the start of the game you can’t really afford a nucleus, you just have a small prokaryote which spends most of it’s power on a flagella and a couple of other organelles.
But then if mitochondria make 75 atp/s then once they are unlocked it rather changes things. Then you can make what is now the starter cell without too much difficulty using the new, much better, powerplants. On some googling it seems that mitochondria are pretty much required for being a eukaryote so it’s reasonably realistic and makes good use of O2 and the GOE.
“Most eukaryotes have mitochondria, while every multi-cellular eukaryote does. However, a few one-celled eukaryotes lack mitochondria. All of this type of eukaryote live as parasites.”