In Terraforming Mars, you control a corporation, and you buy and play cards describing different projects.
The projects often directly or indirectly contribute to the terraforming process, but can also consist of business enterprises of different kinds. In order to win, you have to accumulate a good terraform rating (TR) and many victory points (VPs).
Your TR is increased each time you raise a global parameter (temperature, oxygen or ocean). Your TR determines your basic income, as well as your basic score. As the terraforming process proceeds, more projects become feasible. Additional VPs are awarded for anything enhancing mankind's grip on the solar system. This can be anything, from founding cities to building infrastructure, or protecting the environment. â€¦