I'm glad you enjoyed it!
I really like the idea of keeping health between levels - that's something I'm looking into. It'll be a while before I get to that, but I agree that would help amp up the challenge. More characters, enemy types, and bosses are planned too!
Fire Emblem Heroes is a huge inspiration for this game, but without the powercreep and the gacha elements, so I'm happy to hear you mention Fire Emblem.
Thanks for the feedback!