Zarya-1 plays like reading the script of am audio dra,a in "Choose your own adventure" style. You are guiding a team of four astronauts who have been sent to the moon to investigate strange radio signal. The game is presented through dialog between the astronauts and about a dozen still images. Occasionally you get to make a choice between 2-3 different things to say.
The writing is really good, the characters are distinct, and there is well-designed sense of mystery that keeps the player going. The physical conditions of an airless low-gravity environment are described in an interesting and illuminating way. Occasional scary or humorous moments provide suspense and comical relief in well-paced alternation. The game really makes you feel like a mission commander whose decisions will determine the fate of your team. It could have benefited a lot from voice acting, but at this price point, that can hardly be expected.
On the flip side, there is barely any gameplay. Most of your decisions are just fluff and don't affect the story at all. The game tries to create a sense of urgency by giving you the impression that time and air are limited, but it cannot actually keep track of these resources, and your decisions do not really affect them. Also, paradoxically, the "perfect ending" is hidden in a side track behind pretty arbitrary decisions.
I enjoyed the story and atmosphere, but wouldn't recommend approaching it like a puzzle or simulation, it simply doesn't have the mechanics for that.