SimEarth is a game developed by Will Wright (William not Wilbur) based on James Lovelock's Gaia hypothesis. The manual describes it is an informative toy and entertaining activity on top of that. And this says a lot about the game, there is no story or actually even no goal.
At the beginning you can choose a starting planet, which has an influence on the starting point. After the planet has been created you get to read a short text giving you some hints about the current situation. And off you go! I for one always make up my mind on what I want to achieve in my game sessions, but for doing so it is really important to know a bit about the game first. Usually (except for Daisyworld) there are seven different kinds of biomes and fifteen different life forms.
All of the species can evolve intelligence. At this point they found a civilisation. Those start in the stone age and eventually end in the Exodus. That is right, the creatures just (literally) take off by mounting their cities on rocket engines. But do not be afraid that does not mean the game is over, you can just turn the next species intelligent after that. Depending on the level of difficulty it is not always that easy to pull this off. One way to create intelligent life is by using a monolith. Unfortunately they cost 2500 Omega points and beginning with normal difficulty you can have 2000 of them at most. So you will have to take the more common way, which means those creatures have to discover fire. A forest fire might be helpful, and there are tools for this (and other disasters) which will cost you Omega.
On top of that you can tune the simulation model. For example you can adjust the axis tilt or tectonic activity. That is also one way to play the game: Simply turning the parameters of the model to the extremes and hope that something useful comes up.
From a technical point of view there is not that much to criticise, considering the standards of the time. You should choose the 640x400 resolution during the installation or things might get confusing. You can install the game in other languages than English, but not alles was translated properly. The CD version of the game takes up a whopping 1.3 MB and features the same content as the disk version.