After some time playing it (0.0.5), I have some thoughts for this rough cut:
Essence and Cores: Should have more than one way to get them, for sure. If you can carry them, you can find them or obtain them. Tasks, quests, barter, etc.
Time shards: I'm okay with this mechanic provided there's a serious reason that consistently gets applied. Again: if they can be gained, they can be exchanged or earned in various ways.
Bigness and Smallness: These both have to have serious meaning, otherwise the whole setting is a glorified Clicker Game. That your friend there starts as huge to begin with is kind of a false start. What is drawing people to be so huge, and how does entropy work in that situation?
We're the MC, so we should have agency and ambitions, too: We should feel weak, small, and want to grow, as well. Or, perhaps there are other ways to realize whatever ambitions we could have as the player. Anyways, can't say I'm in love with the model, but keeping cores for myself would be nice.
Font (personal peeve): Change the GUI font as fast as possible!
Growth animations and mechanics: A little opaque right now, but if there are sectional responses to the beam - our subject, whoever it is, should be able to stand still so we can aim. The wobbling effect should be a bit more subtle, but it's a good indicator of activity.
World: The pop-in on the flora is dramatic. As well, while it's a small time loss - preventing the clock from starting until the scene is loaded and we can orient ourselves in the game world would be nice.
Finally: .....would love some equal opportunity stuff, maybe if you have someone on the team if it's not your thing.