I love this! Simple and addictive. After many tries, I reached an undefeatable state with this combo:
1-2x Shoot 6 bouncing bullets
1-2x Next attack shoots twice
1x Refill energy to full
1-2x Stop enemies for 2 seconds
... The rest of the deck padded with 0- or 1-cost cards
+ Bouncing attacks pierce
+ Regenerate hearts
+ Pick from 4 cards
I could manipulate my hand so that I could just hammer a single key and cycle through my deck as fast as I wanted, wiping all enemies from the screen while they were frozen in place! Very satisfying to pull off.