The idea is to code the behaviour of a critter that can move / attack / eat and reproduce.
So a species that survives well can grow and invade a terrarium.
But the cool factor is the blue ball. It is actually a teleporter that sends critters randomly to someone else's terrarium, so your critter can invade other terrariums too :)
Last year as a pet project I ported Terrarium.Net to javascript (this is definitely not noob-friendly at the moment but it is open source :) )
http://terrariumjs.wiselabs.net/
The idea is to code the behaviour of a critter that can move / attack / eat and reproduce.
So a species that survives well can grow and invade a terrarium.
But the cool factor is the blue ball. It is actually a teleporter that sends critters randomly to someone else's terrarium, so your critter can invade other terrariums too :)