Terraforming Mars has been my favourite board game for the past 2 years, and still is. The aim of the game is to terraform Mars by getting all the ocean tiles out, and getting oxygen and heat levels to where they need to be. Plant tiles are also planted and cities built, milestones and awards are achieved, all done mainly by the collecting and playing of cards that do different things. Every card that comes in the game is different. The winner in a multi player game is the one with the highest Terraform Rating, or victory points.
In the solo version it is basically the same game. The challenge is to complete the 3 terraforming requirements before 14 generations, (or player turns). I play with the Prelude expansion which gives a bit of a jumpstart to your game, but it means you only get 12 generations to get it all done. You don't go for points in the solo version, so you don't have milestones or awards.
There is a solo variant, that instead of trying to terraform Mars you try and get a TR rating of 63 or more. With this variant you count up the points of cities and plants and the points on the cards like in the multi player game. I found this variant less challenging and not as enjoyable, so I always play the terraforming way.
I have yet to terraform Mars in 12 generations, I always miss out on the oxygen levels. Next game I try I'm going to focus on those.
My verdict of the solo play: I love it! It is still my favorite game, multi or solo mode.
Here is some photos of my last two games trying out the expansion maps of Hellas and Elysium.
MY SOLO BOARD GAME RANKING with the board games I own
1st Terraforming Mars
2nd Clans of Calendoni
3rd Ganz Schon Clever
4th Castles of Mad King Ludwig