I hate slimes, yuck, glad I managed to kill off some :D
Really fun game, has a bit of a bullet-hell vibe mixed with tower defense which also ties pretty neatly into the theme. I think the gameplay is definitely the strong part here and you can make it a lot better with just some minor tweaks.
Now to the things that bothered me: the grass seemed to big and dense, it blocked off my view and it was frustrating. I would've loved to see the health bar of the slugs and my damage numbers, if upgrades are involved I think players want to see their damage numbers go up.
And finally the mushroom house was kinda small and hidden away, I didn't understand that I need to protect it at first.
Congrats on your first 3D game, you did great and thanks for your feedback as well!