Fun! I would like an option to view the card art closer, it's nice. The lack of audio was surprising, but fine. Certainly better than bad audio.
I think effects that play off of factions other than Knight would be good, as would more 1-mana cards in the drops, and maybe the existence of 2-mana cards. As-is, Mother Slime only gets summoned Turn 3 at the earliest, so by the time her death effect pops, I can afford much stronger things than a knight-equivalent to fill my limited field slots with.
The Trample effect doesn't seem to work; I think it's probably to do with negative health values being allowed.