Thanks for the feedback. We've definitely had a lot of people tell us the first levels are too difficult. I think they were poorly designed because enemies leave the screen and it makes the player feel like they're wasting points/potential upgrades by letting them pass. Doing nothing is often the "optimal" choice to get to the next level which feels terrible.
We're planning on easing the difficulty curve and trying to put more of the difficulty on the bosses, where you can learn attack patterns and make progress by improving your skill, whereas the levels leading to them are more for deciding your build and destroying things.
Game balance is something we definitely need to improve on.