I came here from steam looking for more games by you and, while still a bit rough, seems like a great one.
I know it's just a demo, but it seems the loop is a bit too tight. 5 hands from a deck of 10 isn't much, IMHO I would suggest doubling everything, number of cards, number of copies, number of hands, amount of points to get, everything except hand size I guess. That would give you design space for better cards, while also letting you make removing cards cheaper, Void Tokens instead of Embryos (or keep it with Embryos but 2 per level then have removing only cost 1).
Next, I liked playing with the red cards, but was at the final void by the time I had my deck set. Let use prestige into a red theme deck. That way you can start us off with bad red cards instead of making us go all in on them in order to build that deck. That will leave the design space open for even more decks, I envision a green deck that lets you draw on the cheap with energy management being the constraint, maybe move the druid into that.
Or tell me to eff off, you have made some great games that I really enjoy, you're the genius here, not me :)