Surviving Mars is a city builder based on the idea of colonizing the red planet. In order to accomplish this, the player starts with a small fleet of drones and must extract basic resources such as iron, concrete and water from below the martian surface, while also producing enough electricity to keep the operation running.
However, some tasks such as research and complex manufacturing processes require specialized human labor and for that the construction of artificial closed ecological systems is necessary as Mars lacks an atmosphere and the soil is poison. That's the game pretty much, the objective is to build a self sustaining colony on another planet that's resilient enough to survive a dust storm or a cold wave every once in a while with limited funding. The game has no real end, but there's nothing to do after that beside starting a different colony with different starting paramenters.
Also, this being a Paradox game means there's DLC that adds additional content and objectives, such as terraforming the planet, but I haven't played it so I can't comment on it.
There are other aspects about the game which I think are too pedantic and subjective to even mention, like my opinion on the lame writing and disdain for pop scientists such as Neil deGrasse Tyson, but I digress.
Overall, Surviving Mars is pretty good. Your mileage will vary depending on how much you like dealing with natural disasters or building pretty looking futuristic colonies.