Thank you!
I did think about the card costs in spells. The initial idea was to only use no-cooldown spells for attacking: whatever you draw, you can use, but each card only in one spell. Focus changed away from spellcasting, and disabling cards for spell use would take extra time to code, so it was left in as a positive side effect! And a negative if you had a +5 or something, but it seems too rare to be a downside.
Thank you for pointing out the overpowered-ness of it. I'll look into replacing discards for some of the spells, or just encourage keeping cards more.
And congrats for getting to the bird! It really is the end of the game for now.