I'm really happy to hear so much positive feedback and I'm glad you enjoyed it :)
Sorry about that bug in the first level, it was super annoying but I solved it in the end. I'm still not sure what caused it since I was never able to reproduce it in the Unity editor (weird!) but I implemented a different system for counting enemies and it works much better.
You're certainly right about the cards... I'm hoping to do a little overhaul of the UI and inventory system soon so I'll definitely be looking into ways to make the
Auto-attacking is definitely something I'll consider implementing - I was originally thinking of having gameplay elements that would incentivize not attacking for periods of time (like a perk that makes you build up damage by not attacking for a while, etc.) but as it is there isn't really a reason to let go of left click.
I'll also be looking into adding more ability cards, since I do think they have the potential to spice things up. There is also a system almost fully implemented for modifier cards (you'd attach them to your equipped cards to add extra damage or special effects and stuff) so once / if that gets implemented, it should hopefully add another dimension to the gameplay as well.
Thanks for the feedback, and thanks for playing!