Genetics and Visual Features Inheritance in Paralives

Happy Friday, Anna here!

Today I am going to talk about the genetics system in Paralives, something we started working on a long time ago (back in 2020… time goes by so fast!). I’ve been revisiting the whole system recently to make it work with all the updates to the Paramaker that have been implemented since, and to integrate it into the pregnancy gameplay. A perfect opportunity to show you how it holds up in action!

Note that this post is for Patrons only; please don’t share it. Thank you! 🔒

🧬 Different Types of Inherited Traits 

In real life, our physical appearance is influenced by the genes we get from our parents and lots of environmental factors. Don’t worry if you don’t remember your biology class about dominant and recessive genes, there won’t be a test!

Our main challenge in Paralives was to create a system that lets the player recognize certain traits passed down through their generations of Paras somewhat realistically, without diving into overly complex genetic rules. We wanted things to feel believable, with some fun details (for those of you who do remember Punnett squares 👀) while keeping the system lightweight and consistent with character customization.

We use different inheritance rules depending on the type of trait, and we’re focusing solely on visual aspects here. Let’s go through them!

1. Facial Features: Straight From One of the Parents

Our goals with facial features inheritance are quite simple and definitely not nearly as complex as real-world genetics. We essentially want the player to be able to recognize that “They have their mother’s nose!” or “They have their dad’s jawline!”.

How it works:

For each facial feature (like the nose, chin, etc.), the child inherits all the relevant sliders from one parent, chosen randomly. For example, they might inherit their entire set of nose sliders from their mom, and the cheeks from their dad. This helps keep things coherent and avoids weird mixes of incompatible sliders, which can quickly lead to ugly or extreme results.

Here is our favourite couple from the trailer video and the two children we created from them with the genetics tools of the Paramaker. Aren’t they cute?

2. Height: Partly From The Parents, Mostly Up to Chance

As you know, changing the height of the characters is central to Paralives, and we’ve been trying to make this happen since the very beginning of the development. Having this possibility of different heights adds a lot of uniqueness to characters and makes the world feel more diverse and alive. Our goal for the genetics part of height is not only to get this idea of height being inherited, but also to add some variation to it so that children of the same parents don’t necessarily have the same height. We want the player to say things like “This family has giant genes running in it!” or “This child grew to be taller than both their parents!”. Waiting for kids to grow before knowing which one is going to be the tallest of the family is a nice little detail that this system makes possible!

How it works:

We split heights into three categories: short, medium, and tall, with different ranges depending on the Para’s sex (resembling real-life statistics). When generating a child’s height, we randomly pick one parent’s category and apply it to the child. Then we randomize the exact value within that range. That means your Para might be “tall like his mom”, even if they’re not exactly the same height.

The big brother is already taller than everyone!

Note: In the Paramaker, you can make a genetic child from two same-sex parents, but during gameplay, the parental couple will always consist of one para that can get pregnant and one para that can get others pregnant (you can edit these per character in the Paramaker).  

3. Eye Color, Skin Color, Hair Color and Texture, Freckles: Your Textbook Dominant and Recessive Genes

For those traits, instead of getting the direct value from one of the parents, we wanted to build a more complex genetics system that reflects simplified dominant/recessive models that are already documented in real life. These are the only traits that are able to “skip a generation”! 

How it works:

We built a simple system of genes and alleles to simulate how these features are passed down. Some traits are dominant, meaning they only need one copy of the gene (allele) to appear (like brown eyes). Others are recessive, which means they need two matching alleles to show up (like blue eyes). I already talked a little about the two-gene model for eye color in this very old post, but here is another example that we implemented for hair texture.

There’s one gene for hair texture, and it can have four possible alleles: straight, wavy, curly, or coily; with coily being the most dominant, and straight the most recessive. In other words, the more curls you have, the more likely the trait is to "win" when mixed. Let’s say a Para gets one curly allele from their mom and one wavy allele from their dad. Since curly is more dominant than wavy, the Para will have one of our curly hairstyles, chosen at random. But the wavy gene is still there, and it could show up again in their child, if paired with another recessive allele!

In this example, the mother’s hair is coily and the father’s hair is straight. In genetics terms, the dad has to have (Straight/Straight) alleles, since straight hair is never dominant. Since the kid has curly hair, it means his mom has (Coily/Curly) alleles and he has (Curly/Straight) alleles. 🤓☝️ One curly grandpa or grandma would have been very proud!

👩‍💻 Application of the Genetics System 

We use the genetics system in several different situations: 

• When creating a Para from scratch in the Paramaker: The game analyzes their current features and deduces the genome data corresponding to the actual look of the character. If the character has “unnatural” traits (like pink eyes or green skin), their genetic data is randomly assigned.

• When creating a Para from two parents: Whether you’re in the Paramaker or Live mode gameplay (by getting pregnant), the game generates a child by following the inheritance rules we’ve explained above, from the genetics data of the two parents.

• When adding a parent or sibling in the Paramaker: The system uses existing genetic data to generate the new family member so that everything fits together nicely.

• Not implemented yet (but might be an update in the future): An advanced genetics interface for all the geeky players out there wanting to control their Para’s genetics themselves. 

🍼 Note: Babies and toddlers don’t have access to full sliders, so their features might look a bit generic at first. But don’t worry, their genetic data is still computed and saved, and once they grow up, they should reveal their true heritage!

Here is the updated look of the interface for creating characters with genetics! Note that right now, only two options are available (Create Child, Create Twin), but there should be more soon (Create Parent, Create Sibling). You can choose the sex and the life stage of the child you want to randomize. 

🛠️ Hacking Your Para’s DNA With the Mod System

As with most of our in-game systems, genetics are widely moddable. You can add, remove, or modify any trait category that supports genetic inheritance, set up the sliders you want inherited (or not), and more. 

Some examples of applications could be:

• Create a new alien species with green and grey skin tones (with green as the dominant color)

• Make “unnatural” colors (like bright pink eyes or blue skin) inheritable

• Add new accessories, like devil horns or Shrek ears, and make them inheritable too (pretty sure Shrek ears would be a dominant trait, in my scientific opinion)

Do you have any other ideas for genetic traits that you would like to mod in Paralives? 👀 I’d be happy to hear them!

There are many little details we are still working on to make the most believable and good-looking children Paras, but I hope you enjoyed this little tour of the genetics system to date!

That’s it for me!

Have a wonderful weekend, 

Anna