One piece of feedback I'd say: When you have cards that Retain, they shouldn't reduce your card draw at the start of the next turn.
Oh actually, one more thing, unless I'm mistaken, in more cases than not, the higher cost card that triples its upgrade seems functionally the same as the cheaper cost card that adds 3 when its upgraded. This makes the higher cost card not worth it compared with the other.
(but like I said, I may have just not found the use-case where it's better)
I largely agree with both of what you said but theres a few things to consider,if they dont stop your draw whats stopping you from taking every piece of quartz (retain resource) you see plus some draw and a aquifer or 2 ( action that upgrades every card in your hand by 1)? So it feels to me that they will need some kind of downside to make up for them not stopping draw
as corite (2cost +3 to your upgrades) vs cube (3 cost X3 on your upgrades)
you can use tools to bypass the energy cost so paying the actual cost should be rare, for almost every upgrade card coreite actually upgrades more then cube 1+3 =4 vs 1*3 = 3 and that feels really dumb but there are some cards that do upgrade cube more though jerb ( the kangaroo rat thing) that hits random targets by 3 (3x3 = 9) you can control him kinda by removing ores with tools for example and having actions in your hand that they cant upgrade. Corkscrew 2 cost so expensive but 3 on the upgrade and hammer upgrade in the store.
overall i think that corite is better and thats the cheaper one so that feels very strange for me