the idea is simple
there is a terrarium (a box)
inside the terrrarium there is a critter which lives forever
the terrarium have a refuel station able to recharge critter batteries
1) when the critter is full of energy it lives:
roam the terrarium and interact with enviroment :respond to sounds, make sounds, blink lights according ecc
it's able to detect environment light level then respect a day/night behaviour cyle
2) when the critter is low battery it head to refuel station and acquire electrical lock with it