Super fun! I managed to beat the first boss on my third try.
I think the graveyard shovel may be buggy. It allows me to put a card back in my playing lane but, after I use the shovel, all my remaining cards just have the discard action.
Other thoughts. I was a bit irked that my remaining resources reset after each round. The game would undeniably be easier if you kept your resources but it would also permit some multi-round strats like saving up for an expensive card. I'm sure you considered this though and balanced the game with this in mind.
The description is off above "Then if minions exist in the lane they will attack" should probably be "monsters"