I think one of the key elements that will be needed to make 2D Multicellular more fun is a natural incentive to evolve different specialized cell types. For example, there ought to be more benefit to a single cell with lots of digestive power versus many cells with only a little digestive power.
Additionally, another method is to make placement of cells matter more. Make damage affect the outermost cells first, so the player is incentivized to evolve their outer cells to be their skin cells / protective cells. Make neural cells grant a bonus to adjacent sensory cells, but make sensory cells ineffective unless placed on the exterior. Make digestive cells grant a bonus to adjacent absorptive cells / feeding cells.
With these two elements, the player will have to think more carefully about what cell types to evolve, and also where to place them in his colony. This will only apply to 2D Multicellular, because after the transition to 3D we will no longer simulate individual cells and the player’s creature will be organized into a series of tissues instead.
Finally, I think it would be good design to ensure that any mutations we consider adding to flesh out the cell types be available in both Microbe and Multicellular. It doesn’t make sense for an organelle to just appear only for colonies but not evolve in unicellular life.
Since this is a topic that can be implemented soonish, I think it would be good to have a discussion and nail down the concepts, and then document it on the wiki. However, to be clear, I’m not pushing that we do this right away. This is meant just as a design discussion to document some concepts which we can refer to later when we actually get to implementing this. I’ll start by listing all of the common biological “cell types” that we will want to incentivize the player to evolve:
- Skin Cell / Protective Cell. Cell types that focus on protecting the colony as much as possible.
- Absorptive Cell. Cells that maximize their Phagocytosis Ability to be able to engulf the largest possible particles from the surrounding water, that the colony can then eat.
- Digestive Cell. Cells that maximize their digestion efficiency and digestion speed to extract the max amount of nutrients from the food the colony eats.
- Locomotive Cell. Cells that focus on producing locomotion for the colony through cilia, flagella, mucilage jets, or other means.
- Endocrinal Cell / Hormonal Cell. Cells that maximize the production of agents, either for internal or external use.
- Storage Cell / Fat Cell / Adipocyte. Cells that maximize their storage space to store the colony’s food.
- Biosynthetic Cells. Cells that generate sugars or other nutrients (like ammonia) for the colony, using Photosynthesis, Chemosynthesis, or Thermosynthesis.
- Sensory Cells. Cells that focus on maximizing sensory reception.
- Neural Cells / Neurons. Cells that focus on maximizing nervous capacity / signal proteins.
- Muscle Cells / Myocytes. Cells that are very fluid and flexible that maximize movement speed through contractile fibers.
- Bioluminescent Cells. Cells that focus on producing light biologically.
- Gametic Cells / Reproductive Cells. Cells in a sexually reproductive colony that focus on produce gametes.
Then we can discuss these cell types one at a time. What are the incentives to evolve such a specialized cell? What mutations would such a cell utilize? What traits would it try to maximize? Should it have any placement/adjacency effects? I’ll start with the Protective Cell:
As far as I know, damage to a colony only affects the outermost cells right? So the base incentive for this is already in place. The player will naturally want to evolve his exterior cells to be the most damage resistant.
What are some mutations that skin cells would evolve?
Scientifically speaking, there are not many mutations a skin cell will evolve at this point. It’s only when organisms get much larger that they will evolve many many layers of skin, with perhaps additional layers of scales, shells, and more.
When an organism is microscopic and soft-bodied, the best he can do is just evolve a layer of useless outer cells to sacrifice if he is ever attacked. These cells would have as few organelles as possible so that they cost as little as possible to maintain, and just serve to be the first line of defence. In Thrive, since we aren’t going to model the individual death and regrowth of cells in a colony, the benefit of skin cells will just be that they increase your overall health.
The alternative is to not be soft-bodied and evolve cell walls. I’ve seen many Let’s Players evolve cell walls for their outer cells, even when playing as very mobile organisms. From what I know this is pretty unrealistic, because any multicellular organisms with cell walls or mineralized shells (calcium carbonate or silicate) sacrifice most or all of their mobility. Or at the minimum, they keep a portion of their organism uncovered so that they have one region by which they can flap some flagella to generate thrust. So I think to address this the game should look at how many exterior cells have cell walls, and apply a penalty to the colony’s mobility based on what percentage of exterior cells this is.