Now to the one big functional change that I would make if I was in charge... let the player put an ace up their sleeve. I'll will say if you don't agree with this type of change I totally respect that, and what you've got here is already quite fun to play, just sharing my opinion as to what I think would make the game more fun and give players another layer to work with in their strategies, and I think also lead to a more successful game overall.
Ok here's my Ace pitch...
Under the Card Pile and above Energy create a blank card slot, which you can drag a single card to. Maybe you even have to pay the cost of this card to put it there, and then pay again to play it (idk, spitballing)... this card remains here until used.
The single most (and truly, almost the only) thing I find frustrating thing about this game is getting a bad draw on my last hand and losing a run over it because I'm 2 Scorium shy. I'm encouraged to gamble a bit, and risk losing, and I like that... but I don't want to 'have to' count cards to weigh my odds quite so closely. Let me 'cheat', just a little... for a cost. I could go on, but I'm sure you can imagine many use/abuse cases for something like without me selling it any harder. No reason it can't exist but be disallowed in the most difficult settings, also.
Congrats on something well made getting attention, hope to join you in that club someday.