This is such a cool idea! I hope the attention brought to you and your games from the whole thing with the thief more than makes up for it.
The early game is fun but the late game is less interesting if you have a broken deck, because there's no end. I stopped with modifiers to make piercing bullets bounce, regen hearts, and make everything cost 1, and my combo was "next attack is piercing", "next attack is love", "refill energy", "shoot 9", and 1 other non-attack card. the shoot 9 with all these modifications just clears the whole board every time. And the other 3 slots in my deck were just dedicated to reducing the chance of accidentally getting rid of one of my combo cards.
Yeah, it needs an end or better late game content or something. I had a different combo-- shoot an everything bullet+all cards shoot an extra bullet-- but it still ends up with just play your cards at a moderately fast pace and hope you aren't forced to lose your combo on level up and that does stop being interesting pretty quick (especially when you have a redundant copy of each combo piece)
Yeah, same experience here. Just hit my first truly broken combo. The energy-refill rare card is incredibly powerful, as are the freeze cards. I'm still crazy about this game, though, the gameplay loop is incredibly satisfying. If the dev wants to expand it there's a ton of potential in this idea. :)