One of our planned features is an update of the reproductive system, so I'm going to tackle that right now.
A lot of what I say may and probably has been covered in other discussions, especially those on the CPA system. I haven't followed CPA discussions as closely as other topics, so please fill me in if I start going on a branch that has already been discussed.
Currently, cells accumulate a fictional compound called Reproductase to reproduce. Once a cell has 5, bam, it splits, and then the player can enter the editor.
This is the first thing to change. The cell shouldn't reproduce until the player clicks the reproduce button. Also, the player should first enter the editor and make their changes, and then the cell should split after they return to the game.
More importantly though, we want to do away with Reproductase altogether. We're still going to follow the concept of gathering certain compounds to a certain threshold in order to reproduce, but it will be different compounds and a different (possibly dynamic) threshold.
Reproductive Cost (R)
Consider every cell a big network of compounds attached together. We can count these compounds, and thus find out how many you need to make a perfect replica of the cell.
Speaking of compounds, we will have to introduce some new ones that aren't in the game yet, and finally create some purpose for amino acids!
All organelles are composed of amino acids, fatty acids, nucleic acids. Later, we can decide whether it's more accurate for a mitochondria to be composed of proteins than amino acids, but for the time being we'll just use amino acids, fatty acids, and nucleic acids for this discussion.
For easy reference, we'll call them AA's, FA's, and NA's.
Organelles like mitochondria and chloroplasts are composed of AA's and FA's. We will need to define exactly how many AA's and FA's each organelle is composed of. Upgrading organelles can change the composition. For example, upgrading a mitochondrion to have more folds increases the ATP produced from glucose, but also increases the amount of AA's and FA's to build it.
The membrane is composed of AA's and FA's.
The nucleus and surrounding organelles (the nucleic core) are composed of AA's and FA's. The DNA in the nucleus is composed of NA's, but since we don't simulate the DNA, we can just add in the amount of NA's to the composition of the nucleus.
Thus, we can see that your cell has a total amount of compounds that it is comprised of. This sum of AA's, FA's, and NA's is basically the “price” of your cell. If you want to “buy” another cell, you've got to pay the “price”. In terms of Thrive, this means stockpiling AA's, FA's, and NA's. This price will be referred to as the Reproductive Cost or Reproductive Price of your cell, which we will denote as R. Note that although R is one number, it's a sum of different numbers, and you can't build a cell by filling a deficit of AA's with excess FA's. You need exactly as many AA's, FA's, and NA's as are needed.
To anyone familiar with the CPA system, please let me know if there is already a variable for this, and I'll change it to that to avoid confusion, because I know that R is basically Locked Compounds.
When in the editor, it would be good if we could have a display of R somewhere on the UI, ideally broken down to show exactly how many AA's, FA's, and NA's.
Also, I realize that cell walls are made of sugar, so sugars can be part of that cost as well.
Now it's time to make some design decisions. There are two proposed methods for how to reproduce:
The cell gathers the necessary compounds in its storage, until it has gathered at least as many AA's, FA's, and NA's as are needed, if not more. Once the player has enough of these three compounds, they can click the reproduce button, and they enter the editor. After making changes, they return to the game, and the cell then “spends” those compounds to replicate itself. Both new cells now have the changes applied to them.
This plan is simple, straightforward, and has an easy to understand threshold. The drawback I can think of is, say your R was 100, but then you make changes to your cell (e.g. Adding cytoplasm) which causes the R to increase to, say, 150. Then two new cells are created from the replication, with these changes (and thus comprised of 150 compounds each). Does it make sense that you only spent 100 compounds to build a 150 compound cell?
Here's another proposed method.
The cell gathers the necessary compounds, but they do not go into its storage. Rather, when a cell produces AA's, or FA's, it uses them to grow in size. NA's are an exception, because your DNA does not change. Your NA's still need to be collected and stored until you enough to make a second copy of your DNA for replication. You can then reproduce once your cell has reached at least double its original size and stored at least 2x its original amount of NA's. When you reproduce, each daughter cell is half the size of the mother cell, and has half as many compounds in its membrane, nucleus, organelles, and DNA.
This plan is much more realistic, but also creates a problem for CPA calculations. How do you gauge the fitness of a cell that varies over its lifespan in size. Also, as a cell's size changes, doesn't that mean we need to recalculate absorption rate, storage space, processing power, etc?
Same as Plan B, but you can replicate at any time. The drawback to reproducing before you've doubled your size is that the daughter cells are now much smaller and less likely to survive.
This plan is also more realistic, but there is no more threshold that the player must reach to reproduce (unless we put a basic minimum).
Which of these methods should we use?
If not, what methods would you propose?
Another important question to answer is how the player reaches the ability to reproduce. Given this definition, it is purely by gaining a certain threshold of certain compounds.
The following points use the processes listed on the last post on this thread as reference:
Where will the player get AA's from? AA's are produced by the cell from ammonia, and ammonia can be gathered from the environment. Ammonia will often be produced by nitrogen-fixing bacteria. AA's can also leave your cell if you expel
Where will FA's come from? FA's are produced by the cell in the presence of very high amounts of pyruvate (look at the last post on this thread, and pyruvate is produced from glucose, which can be gathered from the environment.
Where will NA's come from? NA's are produced by the cell from AA's and glucose, which ultimately comes from ammonia and glucose, which can both be gathered from the environment.
So basically, glucose and ammonia are the two compounds that cells must gather in order to produce the AA's, FA's, and NA's needed for reproduction.
There is one unanswered question after all of this:
Should there also be an ATP cost to reproduction, and if so, how will we calculate it?