I have been immersed for several days in a game called Waking Mars. I found it through Apple's recommendations I think. From the description I thought it would be something like SimCity but it's not, although there are some simulation aspects. It's a mission based game, and the missions involve gathering information about the various life forms encountered and growing them to build a more or less balanced eco-system. Some of the creatures are friendly, others are dangerous, but they all have their uses.
I love this game, and I highly recommend it for people who like non stressful games involving reflexion and strategy.