In Tharsis, you control four crew members of the Iktomi, a spaceship on a passage to Mars. On the journey, a meteorite hits the ship, causing damage and the death of a two crew members, and the problems don't stop there.
Crew members have up to 5 dice and will lose 1 per week (turn). Dice can be restored in the Life Support room, or by eating food (grown in Greenhouse). Crew members have a health bar, so will die when depleted (restore in Medbay). A stress bar (reduced in Operations room) which dictates the events at the end of each week. The ship has hull strength which can be increased in the Maintenance Room. It's also a good idea to increase your Assists in the Laboratory. Assists prevent you from the effects of Hazards.
With each week, there will be at least a couple of problems that you need to fix. The room will have a number, a penalty for not fixing it by the end of the turn, and some Hazards which make repairing more difficult.
In each turn, you assign your crew members to a room, where they roll their dice in order to fix the problems, or take advantage of their own ability or room ability. The severity of the problem is assigned a number, and your aim to add dice to reduce the number down to 0. Often you will need to assign multiple people to the room depending on the severity, the amount of dice you have, and the luck of the rolls.
The room may also have some Hazards. This means if you roll a particular number, you may take damage (Injury), be prevented from re-rolling that die (Stasis), or may lose the die (Void). When rooms have multiple Hazards, then it can be infuriating and seem unlikely that you can actually succeed.
You can re-roll the dice once, with the Captain gaining an extra re-roll. This can be beneficial in some situations, but you must be cautious against rooms with Hazards. I guess it's always a risk-vs-reward system.
If you have dice left over, you can add them to your research pool. There's an area with slots for dice 1-6. Research is basically a selection of abilities to help get you out of sticky situations, at varying costs. There's a wide range of aspects like extra food, health, assists, repairs etc. These are basically essential when you are hit with some tough problems at once.
Once all crew members have moved, the week ends, and you will take any penalty of the rooms you failed to repair. You then are presented with ideas from the crew members (based on their stress). These also have all kinds of effects which will reduce or increase all aspects. So you might have to choose between two scenarios where one is "two members lose a die, but regain health" or "ship loses 2 hull strength, but you gain 1 food". Keeping all aspects of your crew and ship healthy is pretty much impossible, so you have to make sacrifices and choose what you think you need the most. A lot of the choices are bad either way, but you have to choose the one you think impacts you the least.
The game ends when you have survived the 10 weeks, your crew members all die, or if your ship is destroyed.
There are many unlockable crew members which are unlocked when performing certain actions. Many of these seem a bit high, forcing you to repeatedly play the game in order to unlock them. Aside from the story mode, there's some set missions which put you in various scenarios and you may have to survive for 5 turns or whatever the victory condition is.
I did enjoy the game, and it is good to replay a few times to try and achieve a better score. However, the game is pretty short, and there's only so many times you can replay it without getting bored. At a low price, I do recommend it.