Thanks for the feedback! I'm glad to hear it's running well in your browser, as I was not getting as good of performance. You are also right on with the target audience; Slay the Spire was my biggest motivation for making this game.
There will definitely be a UI redesign of the battle scene, as it's not intuitive, even for those familiar with the genre. The card 'spaces' add another layer that needs to be communicated to the player, and I'll keep experimenting with how to do that. I hope you still experienced a few moments of fun.
I appreciate you taking the time to look at another deck-builder while working on one. Thanks again, and good luck on your game, too!