Thank you for your feedback!
Unfortunately we missed the first 1.5 weeks so we couldn't implement and balance everything as planned. Originally the mushroom was supposed to sit in the middle of the screen, with enemies coming from both left and right. As you can probably imagine, we also had more interesting enemies planned, demanding more interplay between your weapons and shield.
In the same vein, the skill tree isn't nearly finished right now and the map has nothing in common with the one we originally planned (progress was supposed to be much more explorative and procedurally generated) . We simply ran out of time.
You must have been rather lucky with your stats if you had no problem progressing whatsoever at any point. We always had some point at which we couldn't progress without repeating one or two levels. :)