Solid premise, but there's very little strategic depth as I could usually just level up all my characters and blindly upgrade whatever and still win comfortably every time.
There's some mouse detection issues with the UI which does put a damper on the experience, and when I didn't have enough coffee to buy an upgrade I also mistook that for a UI issue since that was not communicated clearly enough.
With some more thought given to difficulty scaling and strategy, this could be a lot of fun!