Hey ya'll! I'm doing a study on the Chao Garden from the Sonic Adventure series. I have fond memories of the systems in this game, and I hope you learn something!

I'll be focusing on the SA2B version of the game on PC. There are a ton of version specific nuances that exist.

Mechanics

The Chao

Couldn't say it better than they explain it here: Learn the basics about Chao - Chao Island

"Chao made their first appearance in Sonic Adventure in 1999 (December 23, 1998 for Japan) as a launch game for the Sega Dreamcast. Chao (pronounced “chow”) were given a canonical history within the existing Sonic universe. Chao were seen to have existed since an ancient time, protected by a creature named Chaos; who was also the original guardian of the Master Emerald. The player has been able to raise Chao for themselves in all the Sonic Adventure games, as well as a few other Sonic titles. The Chao are an evolution of the ‘A-Life’ system that Sonic Team originally created in the Sega Saturn Game “NiGHTS into Dreams…” using small creatures called ‘Nightopians’. The Nightopians would change their behaviour depending on their treatment. You can raise Chao in-game in special environments called Chao Gardens; special protected enemy-free sanctuaries designed for the safety and well-being of the defenceless Chao."

Official Sega Sonic Adventure 2 Chao pre-release screenshot Official Sega Sonic Adventure 2 Chao pre-release screenshot Official Sega Sonic Adventure 2 Chao pre-release screenshot

"Chao hatch from eggs and grow through infancy into maturity. However, the way you care for your Chao will determine its physical characteristics, behaviour, personality, and way of life. These Chao create a very unique ecosystem and learn and breed according to what you do. You must help your Chao to live by providing it with the necessary things such as food and attention. Chao have become a popular character within the Sonic series, both from their appearances in the Chao Gardens and noteworthy cameos. This was greatly helped by the Sonic Adventure series being ported from the Dreamcast to the GameCube, PC, PS3, and Xbox 360 - opening the doors for a very large audience of people raising Chao, and ideally Chao Island should give them all the help they need."

Most of the information I got on the Chao Garden is from this source: Chao Island

Essentially, the player decides how an individual Chao develops. All the way from egg to afterlife and across generations!

A Chao, fundamentally, is a creature made of several components:

  1. Stat values
  2. Personality/emotion values
  3. Genes
  4. Alignment value
  5. Evolution strength value

Brief descriptions:

Stat values are numbers tied for various attributes (e.g. Fly, Run, etc.)

Personality/emotion values that influence behavior. The game runs on some sort of clock system, so these values change the likelihood of certain behaviors when the game decides a Chao wants to do something.

Genes are used in the breeding system to determine several traits (especially visual ones) for a Chao that influence it throughout the aging process.

Alignment is how "good" or "bad" a Chao is, or more accurately whether they're team "Hero" or team "Dark"

Evolution strength determines whether a Chao will evolve, and if it's an adult it influences how much it will express its stats as physical traits.

Stats

Each Chao has stats corresponding to seven different abilities:

Swim, Fly, Run, Power, Stamina, Luck, and Intelligence

Stats can be leveled up through giving the Chao small animals, chaos drives, or fruits. Their stats affect their performance in mini games, which is expressed in how they look and act throughout their life.

Each stat has a grade which describes how quickly the Chao improves its abilities in a particular stat.

When standing next to a Chao, there's a progress bar for each stat's level. The level value describes the Chao's abilities in the game.

Swim 🟨

Determines how well a Chao can swim, if at all. Represented by the color yellow with yellow group animals and yellow chaos drives.

At level 100 Chao learn to swim. Before that they flail in the water.

Swim is the defense stat in Chao karate

Fly 🟪

Determines how well a Chao can fly. Represented by the color purple.

Flying is used in races when jumping off of great heights, and a higher flying stat increases speed and distance. Most flying sections are short, but making great use of them lets you skip whole sections.

Flying corresponds to dodge chance for Chao Karate

Run 🟩

Determines how quickly a Chao walks or runs. Represented by the color green.

Immensely important stat in all races because all races have land sections. A Chao with low run will crawl, a Chao with high run will walk or run.

Power 🟥

Determines how well a Chao climbs walls and shakes fruit loose from trees

Increases Chao attack power in Chao karate, changes to spinning punches and kicks at high power.

Stamina

Determines physical durability of Chao (size of its "energy" bar)

Only increased by fruit

Luck

Hidden stat

Basically meaningless to the player in game, used to change the random occurrence of version specific things.

Intelligence

Hidden stat

Chao solve specific puzzles faster in a race, doesn't seem fully implemented?

Grades

Each stat has a corresponding grade. Determines how much potential a Chao has in each stat by determining how much it gains from leveling. There's also random variance of 5 to a stat on every level up (-2 to +2).

Can't feasibly get a perfect Chao, but an S rank in the category gets you pretty close!

Small Animals

Improve stats of Chao and give them animal parts! Found in SA stages Give a small animal to a Chao and they will gain/lose stats based on the animal They also learn an "action". They obtain a random amount of animal parts, selected from: arms, legs, tails, wings, ears, and various head decorations.

Supposedly, it's quicker to farm small animals rather than chaos drives for stats early on.

SA2B animals
Image Name Type Swim Fly Run Power
Penguin Swim +36% +12% +8% -24%
Seal Swim +40% -16% 0% +8%
Otter Swim +44% -4% +8% -16%
Peacock Fly +12% +48% -16% -12%
Parrot Fly 0% +48% -20% +4%
Condor Fly +20% +60% -24% +16%
Rabbit Run 0% +8% +40% -16%
Cheetah Run -8% -8% +40% +8%
Boar Run -4% -12% +32% +16%
Bear Power +8% -16% +4% +36%
Tiger Power -8% -16% +20% +36%
Gorilla Power +4% +8% +4% +40%
Skunk Random +8% +12% +12% +8%
Sheep Random +8% +12% +20% +20%
Raccoon Random +20% +12% +4% +8%
Dragon Mythical +20% +4% +8% +32%
Unicorn Mythical +16% +12% +36% 0%
Phoenix Mythical +12% +32% +4% +16%
Half fish Ghost +32% 0% +8% +24%
Skeleton Dog Ghost +8% +8% +32% +16%
Bat Ghost +8% +40% +8% +8%

Chaos Drives

Much like animals, are collected parts of G.U.N. robots that can be fed to Chao to raise their stats.

iirc. Can only collect 10 animals or drives at once in each stage so it's painful

Chaos Drives come in four color varieties; Yellow, Purple, Green, and Red, which each correspond to a specific stat.

Yellow increases Swim by 24% of the Chao's stat bar

Purple increases Fly by 24% of the Chao's stat bar

Green increases Run by 24% of the Chao's stat bar

Red increases Power by 24% of the Chao's stat bar

Additionally, each Chaos Drive increases Intelligence, taking five drives to level it up, as well as Luck, taking 2-3 Drives to raise the level by one. Chaos Drives are twice as effective as animals when raising Luck, and just as effective as animals for raising Intelligence.

Chaos Drives when given to Chao, unlike animals, do not give the Chao any new behaviors, nor do they give any animal parts. This can be advantageous for raising a Chao's stats without disrupting their current animal parts.

Personality

Personality Constraints
(Min - Max)
Normal - Curious -100 to 100
Crybaby - Energetic -100 to 100
Naive - Normal -100 to 100
Normal - Big Eater -100 to 100
Normal - Carefree -100 to 100
Kindness -100 to 100
Solitude -100 to 100
Vitality -100 to 100
Regain -100 to 100
Skillful -100 to 100
Charm -100 to 100
Chatty -100 to 100
Fickle -100 to 100

A Chao's personality changes the likelihood of certain behaviors/events

Personalities cause various changes to a Chao's Emotion, or feelings, which are certain values that promote Chao into performing certain actions.

For example, a Crybaby personality causes the Chao's "Urge to Cry" value to increase more quickly than other Chao, causing the Crybaby to cry more often if abused or hurt.

A more subtle example is in the Solitude personality slider effecting a Chao's Loneliness emotion, which promotes a Chao into looking for the player's attention, by either nuzzling up to them or greeting them.

Supposedly, personality might also determine a Chao's face?

Emotion

Emotion Constraints
(Min - Max)		 Effect
Joy 0 - 200 Joy increases when a chao nuzzles against your character. This is achieved through a high character bond, and a high Lonely value.
After a certain level of Joy is reached, the chao will begin to jump around and cheer in an effort to get your attention.
The value slowly decreases during this time, until the behaviour ends.
Anger 0 - 200 Anger increases upon abuse/taking away food. Anger only affects dark chao, by causing them to stomp their feet and throw a tantrum.
High anger and dislike of a character may cause a dark chao to attack the player. Each attack landed decreases Anger by 10.
The value slowly decreases over time, until the behaviour ends.
Urge to Cry 0 - 200 Urge to cry is increased through abuse/taking away food. At high values, the chao will begin to cry.
The value slowly decreases over time, until the behaviour ends.
Fear 0 - 200 Fear is increased through abuse. The chao will cower and make a shivering noise to show it has been mistreated.
A high fear value, plus a high character fear value will result in the chao running away from the player in terror.
The value slowly decreases over time, until the behaviour ends.
Surprise 0 - 200 Surprise is increased through abuse, and decreases over time.
It is currently unknown what behaviour is tied to this value.
Relax 0 - 200 Relax increases when a chao is pet or picked up.
It is used to calculate how long a chao will stay still after being interacted with.
Total 0 - 200 Unused value of unknown purpose.
Sleepiness 0 - 10000 Sleepiness naturally increases over time, and with feeding. A high sleepiness value will make a chao fall asleep.
Sleepiness decreases while a chao sleeps.
Tiredness 0 - 10000 This value increases while a chao is asleep. It causes a chao to act groggy if its sleep is disturbed by the player.
This value significantly decreases near the end of a chao’s nap.
Hungry 0 - 10000 Hunger decides how hungry your chao is.
At 0 hunger, your chao has a high chance of throwing/leaving food.
Desire to mate 0 - 10000 This value will cause your chao to go into mating season. The value increases naturally after your chao evolves into an adult.
Feeding your chao a Heart Fruit will set this value to its max of 10000.
Boredom 0 - 10000 Boredom makes your chao more likely to play with garden/race toys and perform animal/classroom behaviours.
It increases naturally over time, and significantly decreases when performing actions.
Lonely 0 - 10000 This value, alongside a high character bond and a high character distance value makes your chao more likely to seek interaction from the player.
Dark-aligned chao will give a thumbs-up, while Hero-aligned chao will bow.
Chao may also follow you and nuzzle against you.
Tire 0 - 10000 This value increases naturally over time, and will cause your chao to sit down.
If sleepiness is high enough while a chao is sitting, it can fall asleep sitting up.
Stress 0 - 10000 This value causes a chao to always die, even with maximum happiness.
The value goes unused in the final game, and there is no way to increase it naturally.
Nourish 0 - 10000 Nourish is set before an egg hatches, and will begin to decrease after the chao is born.
Currently, it is unknown what this value is supposed to do.
Conditn (Condition) 0 - 10000 Condition seems to prevent Sickness Animations. As Nourish naturally decreases, Condition will slowly begin to increase.
Curiously, it only seems to increase when the chao is sitting still, and not when the chao is swimming or walking around.
Condition will then rapidly decrease as Nourish gradually moves towards 0.
Energy 0 - 10000 Energy makes your chao want to swim, even if they are unable to. As such, they will target the water continuously until the value decreases over time.
Energy will also make your chao move around more in the garden.
This value has a higher priority over Boredom.
Illnesses
Illness Constraints
(Min - Max)		 Effect
Cough -100 to 100 At negative values, chao coughs occasionally.
Goes up to 100 once cured at doctors.
Cold -100 to 100 At negative values, chao will sneeze occasionally.
Goes up to 100 once cured at doctors.
Rash -100 to 100 At negative values, chao will scratch at itself.
Goes up to 100 once cured at doctors.
Running Nose -100 to 100 At negative values, chao will stand with a displeased face.
This sickness goes unused in the final game.
As such, the animation is unfinished and the Doctor's dialogue has some translation issues.
Goes up to 100 once cured at doctors.
Hiccups -100 to 100 At negative values, chao hiccups occasionally.
Goes up to 100 once cured at doctors.
Stomach Ache -100 to 100 At negative values, chao experiences a stomach ache.
Goes up to 100 once cured at doctors.

Chao Aging, Death & Reincarnation

Age broadly describes how long a Chao has been alive, where the Chao is in its life cycle, and how close the Chao is to Reincarnation or Death.

Stages Birth->Childhood->Adulthood->Death/Reincarnation

Age - Chao Island Wiki Good Technical Info on this page

Reincarnation occurs at the end of Chao's life if their happiness is greater than 30 for SADX and 50 for SA2B/SA2HD. When this happens, Chao will enter a pink cocoon (or a grey cocoon on Dreamcast), followed by the changes below:

The Stat Levels of the Chao get set to 1. The Stat Points get divided by 10, rounded down. Personality gets reset. Small Animal Behaviour gets deleted. Randomly chosen animal parts get removed. Lifespan gets reset. Magnitude and other evolution related sliders get set to 0. Alignment will be set to +1 for Hero Chao, -1 for Dark Chao, and 0 for Neutral Chao.

Everything else is kept on reincarnation, including: happiness, classroom lessons learned, race prizes, grades and hats.

Death happens below 30 happiness with a slightly different cocoon

Technical Chao aging mechanics are something I'm currently looking into.

Chao Breeding

Chao Fact File: Chao Genetics and Inheritance - YouTube

These are my notes from this video, so version exclusive stuff is mentioned occasionally.

Dreamcast versions, Xbox and PS3 version (Has gross shiny textures for many-tones, impossible to get in other version)

Key Terminology

Genotype Example

What a genotype can look like:

Left -> Visible; Right -> Hidden

Genetic Traits

Each trait has two alleles for each Chao

Description Normal White Blue Red Yellow Orange Sky Blue Pink Green Brown Purple Grey Lime Green Black
Monotone
Two-tone (adult)

Examples

Building a red many-tone Chao

We need:

  1. Red mono-tone Chao
  2. Normal many-tone Chao

Red Chao's Genotype

Both parents give ONE allele from EACH TRAIT They get 50% of the genes selected from each parent, adhering to dominance rules. If a Chao has equal dominance alleles in one trait, one is randomly selected.

The result average from breeding these Chao 10 times is:

5x Mono-tone Red 5x Many-tone Red

This is because the Tone alleles are always equal weight, so they're selected at random from the parents. The Normal color is recessive, so we always use the Red parent's gene for the visible allele.

Therefore, if we want a Normal colored Chao, we need to breed two Chao with at least one Normal allele each because it needs to show up twice to be in a Chao's phenotype.

Disturbing side note: inbreeding has no effect on Chao because they don't have recessive genetic diseases

Breeding the normal Chao with one of the red many-tone Chao

The Normal Chao's Genotype; Many-tone Chao's Genotype; Expected Results:

75% Many-tone, 25% Mono-tone 50% Normal, 50% Red

Breeding 10x:

Many-tone Normal x3 Mono-tone Normal (White) x3 Many-tone Red x2 Mono-tone Red x2

Monotype-Normal look white, but they don't have the white allele for Tone necessarily

This is about average expected

Shiny Chao Example

Expect 50/50 color and all to be shiny.

10x Random Many-tone with an Emerald Jewel Chao 10x Emerald Jewel Chaos, because the texture trait dominates Tone and Color

Adding shiny though..

Shiny Jewel Chao

Possible Types:

Expected 10x Breeding:

50%/50% Tone 100% White 100% Shiny 100% Emerald

Results:

50% Mono-tone White Shiny Emerald Chao 50% Many-tone White Shiny Emerald Chao

The color actually shows through the phenotype with a Shiny Jewel Chao

Chao Development

Fruit

Obtaining

Some grow in the gardens themselves, some can be bought from the black market

Growing the fruit in the gardens and shaking them off the trees is fun :2

Purpose

They all fill a Chao's belly

All fruits raise a Chao's stamina

Each fruit can have multiple "bites". A fruit isn't consumed all at once, and the last bite can have added effects.

There are fruits for a lot of different purposes, including mating and alignment

Every Chao has a favorite and least favorite fruit. Forcing a Chao to eat its least favorite fruit (being mean to it) adds in the opposite direction of your character's alignment (makes it less like you?).

Alignment

A hidden number from -1 (Dark), 0, (neutral) to +1 (Hero)

Newborn Chao start with an alignment of 0 Fruits change alignment, as well as being pet depending on your character. Abusing a Chao shifts its alignment in the opposite direction of the character abusing it.

Gardens also have an effect on Chao alignment, influencing it slowly over time

If the alignment value is

<= -.5 evolves into a dark Chao

-.5 < x < 0.5 evolves into a neutral Chao

=> 0.5 evolves into a hero Chao

The "White" Chao is actually a Mono-tone "Normal" Chao. This leads to another mechanic.

Petting a Normal-colored Chao with a "Dark" character gives it a red-ish tinge. This is because the Normal gene allows a Chao to change color based on it's type and alignment later in life. This is special to the Normal type Chao.

Actions that affect alignment
Action Hero Characters Dark Characters
Petting with Heart appearing +0.05 -0.05
Picking up Chao with Heart appearing +0.033 -0.033
Give fruit with Heart appearing +0.01 -0.01
Give fruit with Heart appearing (Child) +0.025 -0.025
Give Animal or Chaos Drive +0.01 -0.01
Give Animal or Chaos Drive (Child) +0.025 -0.025
Chao eats the last bite of Hero Fruit +0.150 +0.150
Chao eats last bite of Dark Fruit -0.150 -0.150
Chao given a fruit they dislike -0.1 +0.1
Take fruit away from Chao -0.1 +0.1
Throw Chao -0.066 +0.066
Attack / Jump on Chao -0.1 +0.1

Evolution

Evolution - Chao Island Wiki Term for any change of appearance for the Chao

"First Evolution"

Chao enters a cocoon where baby Chao transforms into an adult

Marks mating and permanent change in appearance

It locks a Chao into an alignment and evolution type until reincarnation

The first evolution picks one of 5 ability types and one of 3 alignments for 15 total first evolutions. Chao are commonly named with the alignment/ability type format (e.g. Dark/Run) First evolution Increases Chao grade by one rank in the type they become, with Normal-type and Chaos Chao increasing the stamina grade. One of its alleles for the Chao's rank DNA gets the new rank. First Hero/Dark aligned Chao opens up the Hero and Dark gardens. There are dark and hero races as well.

Stat Influence

It's commonly believed that a Chao evolves into the type with the highest corresponding stat, but it's actually based on stat sliders that determine stat "influence".

Chao Level 99 in fly and 5 in others, not guaranteed a Fly Chao.

First evolution determined by alignment and stat "influence" Ability after first evolution determined by stat sliders

If a Chao's stats are in a colored zone on evolution, that's the form it'll evolve into!

Notice there are traits on opposing sides of two axes. By increasing power you're taking away from the likelihood of the Chao being run.

Swim<=>Fly Run<=>Power

In equal magnitude case for evolution, the values resolve as: Swim > Power & Run > Fly > Normal Might notice a slight preference towards Swim type

Evolution Strength

Chao evolve and enter its cocoon when its Evolution Strength value becomes full. Value from 0 to 1 for child Chao. Born at 0, evolves when it reaches 1. Only increases in value as a Chao ages and eats fruit. Increases by 1/60 every 2 minutes. 3 hours for non-fed Chao to evolve, each bite takes about a minute off.

On evolution resets to 0 and increases up to 1.2 which dictates Gradual Evolution. Roughly 12 hours for 1.0 and 14.5 hours for 1.2, 4x as long

Hero garden the strength over time is doubled Dark it's removed

Gradual Evolution

Changes that Chao go through with animals and chaos drives over the aging process

Influences first evolution and second evolution Alignment isn't a factor in second evolution

Old Chao react to stat changes much more dramatically

The Gardens

Unlock

To access these gardens, one must find a Chao Key in an Action Stage to access the Chao World's Chao Lobby. The character who is played within the action stage will be the one to enter the Chao World; they will also be added to the character select found when accessing the Chao World through the stage select. Each character must find a chao key before they can enter this way, but only 1 character is required to access the Chao World via the stage select.

Unlike SA1, the Chao gardens do not contain the Black Market, nor do they have the Chao Transporter option to rename chao. These are instead located in the Chao Kindergarten.

The Chao Garden

is a garden located on the main level of the Chao Lobby, directly in front of the portal where the player enters the Chao World. It is the player's first garden and is unlocked by default, and contains the only entrance in SA2 to the Chao Stadium. The garden consists of a regular hilly grass floor, with a cliff featuring a waterfall cave with a pool at the bottom.

While in the Chao Garden, second evolution strength increases over time as well as via feeding. Alignment does not change over time within this garden.

The Hero Garden

is a garden located on the upper level of the Chao Lobby, up a set of stairs to the left of the Chao Garden entrance; however, this can only be accessed once the player has obtained a Hero chao through the evolution of one of their own child chao; transferring a Hero chao to their save file will not work. The garden consists of several ruins and pillars, with a pool in the centre with a fountain.

In the Hero Garden, second evolution strength increases twice as fast as that of the Chao Garden. Alignment also increases over time for the Chao in the garden, meaning Chao become more Hero-aligned, discussed in further detail on the Alignment page of this wiki.

The Dark Garden

is a garden located on the lower level of the Chao Lobby, down a set of stairs to the left of the Chao Kindergarten entrance; however, this can only be accessed once the player has obtained a Dark chao through the evolution of one of their own child chao; transferring a Dark chao to their save file will not work. The garden consists of several tombstones with a red pool in the centre, with the default 3 garden trees appearing dead but still bearing fruit.

In the Dark Garden, second evolution strength does not increase over time; it is only increased via feeding. Alignment also decreases over time for the Chao in the garden, meaning Chao become more Dark-aligned, discussed in further detail on the Alignment page of this wiki.

Kindergarten

Accessible from the Chao Garden hub world Consists of a few areas:

  • Kindergarten
    • Function: Hub area
  • Health Centre
    • Function: Check for illnesses/conditions of your Chao
  • Classroom
    • Function: Learn "actions"
  • Fortune-Telling House
    • Function: Naming Chao
  • Black Market
    • Function: Used to buy various items, such as eggs, special fruit, seeds or hats
  • Principal's Room
    • Function: Effectively a tutorial for beginners learning about Chao

Closing

Thanks for reading :)

Love Chao, take care -Quetzl