"BOOLAR!" as they say. Or that's what I'm hearing them say. :D
It's a neat idea, pretty simple in its current state as I'm sure you know. It seems like a solid foundation for adding more character types and cards to up the variety. For me, personally, I'd prefer a goal than for it to play out endlessly, with levels which introduce new things gradually over time, but that's definitely a personal preference sort of thing.