Thanks for playing and for the feedback!
Glad and relieved you reached the upgrades XD I would've loved to add more but since I added them a few hours before the deadline and could only make 2 upgrade screens, I decided to make them available a bit later on - perhaps too late.
I was really wondering whether to leave the collisions or not. Without them it could be too easy, and with them a bit too overwhelming. I think they're probably a good addition to the game but need something to balance them out, as another person suggested here, such as an AOE attack. I actually planned to add a grenade launcher weapon to deal with the larger chunks of enemies, but ran out of time!