A: Vivarium is an interactive demonstration of the evolution of behavior. It shows how beneficial adaptations in behavior tend to spread through a population of lifeforms.
The lifeforms of Vivarium live in a flat, continuous world. Each lifeform is independent and potentially different from all others. They have complete control over their own actions. Lifeforms try to eat food, avoid danger, and replicate. As generations go by, you can see lifeforms adapt to their surroundings as a result of natural selection. Adaptation is not programmed into them by you or by the computer, but emerges naturally from the system.
Q: How do I use Vivarium?
A: Each window in Vivarium represents a separate world. For each world you can control the size, layout, and amount of food available. Add lifeforms to the world with the Options menu. You choose what senses and actions a lifeform has. Senses give a lifeform information about its surroundings. Actions are things it can do in response to its surroundings.
Once you have lifeforms in a world, set time to active. This lets lifeforms move about, eat, or do whatever else they choose. If you set time to frozen, they stop in place until you let them go.
Observe the lifeforms. Some are better at finding food and avoiding danger than others. The ones better adapted are more likely to replicate. Children of lifeforms are nearly exact copies of their parents, so they inherit their parents' survival abilities. Competition among lifeforms means that only the best adapted are able to replicate themselves. This competition builds on itself through generations, until lifeforms are very good at doing what they need to do to replicate.
Each generation is subject to mutation. Mutation is a random change in the rules that a lifeform follows. Good mutations help lifeforms survive, and are preserved through generations.
Q: How can I make changes in a world?
A: You can move lifeforms around in a world by clicking on them and dragging them to where you want them to go. To select more than one lifeform, drag a rectangle around them. The standard cut, copy, and paste operations also work on lifeforms. You can move lifeforms between worlds by copying them from one world and pasting them into another.
You can add your own selection to the process of natural selection. You can select and clear any lifeform that isn't behaving as you would like. Or, you can duplicate a lifeform you especially like.
Q: How can I find out more about a lifeform?
A: Double-clicking on a lifeform (when time is frozen) shows more information about it. Energy indicates how well a lifeform is getting along, the higher the better. Lifeforms are constantly losing energy to their metabolism, and every action they take (moving, turning, etc.) requires additional energy. If energy reaches zero, the lifeform dies. Lifeforms gain energy by eating. If a lifeform has enough energy, it will reproduce. Age shows how many tocks have gone by since the lifeform was born. Very old lifeforms can die of natural causes even if they have plenty of energy. The senses and actions listed show how a lifeform can find out things, and what it can do to respond to its surroundings.
Q: What should I look for?
A: Watch lifeforms learn what to avoid, what to bypass, and what to avoid. The first behavior lifeforms usually learn is to seek out food. Some lifeforms will turn and get food nearby, others will blindly pass it by. Those that do not find food efficiently are not long for their world. Lifeforms will also learn to avoid mountains. If they spend their whole life staring at a mountain face, they are not likely to reproduce. Finally, they will learn to avoid predators (if there are any). This is easier if they remain a moving target. Remember the lifeforms you create know nothing about their world, and every intelligent action that you see (such as avoiding mountains) must have been learned through the generations.
Q: What does the Time menu do?
A: The time menu controls the flow of time. In frozen mode time is stopped. This allows you to move lifeforms about and examine them (by double-clicking on them). In active mode time progresses, so lifeforms are able to live. Warp is the same as active except that the action is invisible so that life can move along faster. Step allows each lifeform to live for just a moment, then freezes the world again. You can use the ice cube pointer instead of the Time menu to freeze an active or warping world.
Q: How do sexual Vivarium lifeforms replicate?
A: Every sexual lifeform is both male and female. When a lifeform reproduces, it looks around itself clockwise for the first available lifeform to act as a father. The mother creates a new lifeform using entirely her own energy. The behavior of the child is a combination of the mother's and father's behavior. Sexual replication, as well as asexual, results in fraternal twins.
Q: What does the metabolism number mean?
A: Metabolism is the amount of energy a lifeforms needs each time step in order to survive. The more and better senses and actions the lifeforms has, the higher its metabolism. While it might benefit a lifeform to have the best senses and all kinds of actions, the cost in metabolism means that it will have to eat much more than less well-equipped lifeforms in order to make it.
Q: How far can lifeforms see and smell?
A: Medium vision allows a lifeform to see two cells ahead, two cells ahead and to the left, and two cells ahead and to the right. Short vision is one cell and long vision three cells in the same three directions. Weak olfaction senses one cell in all directions, strong olfaction two.
Q: How do rules work?
A: Lifeforms obey every rule listed at every time step. If two rules contradict each other, the one farther down in the list is obeyed. Lifeforms can only take one action each time step. The action that they take is the first one in the list of actions that they decided to do, and are able to. For example, a lifeform will replicate whenever it can because replication is the first action in the list, and the first rule is to try to replicate. They only time a lifeform won't replicate (when replication is possible) is when a rule farther down in the list decides the lifeform should not replicate.
