BioSys is a biology/environment simulation and "Myst"-like adventure game that gives you control over 4 different biospheres (a closed, self-regulating systems containing ecosystems) to experiment with.
You take over the role of Allan Russell, a genetics professor and environmental activist who lives in a complex of four giantic greenhouses named Biosphere4. They each contain complete ecological system (rainforrest, savannah, ocean and accellerated evolution) which have different needs, animals and fruits which you can eat if the biome is healthy.
After some horrible events you wake up in the rainforrest and have to survive in and escape from the complex. To accomplish this you will have to keep the ecological systems alive (for your food suppply) and even reanimate one biome in order to flee.
Never again, before or after, I have seen a game teaching so much about environmental connections by simply using the human play instinct! Every piece of technological equipment supporting the ecological systems can be controlled by the player, directly on location or by the Bio/SYS 4 - GUI. The impact is fed back by a bunch of sensor data and an overall "condition".
In the course of the game you will discover a background story of environmental terrorism, a sinister multinational corporation and some "loung-sucking mutant plants".
After all, despite being older than a decade, it is quite timeless and, sad enough, the only of it's kind.