I loved the upgrade system, albeit there was a single item that I couldn't find, which was the bird's feather that wasn't blue.
I felt kinda stupid after I found out it was a bird's feather, and had to look up how to get it. I kinda figured that was how, but could never get close enough to catch a bird, and ironically, you have to have that bird's feather for a larger net.
I hope they keep the upgrade system and add some twists into it, like throwing a potion in the mix to upgrade your shield, so you have to collect not only one set of items, but another set.(ie: bugs for the potion, potion + items for the item)