Just saw your post on Reddit on the Godot subreddit. Very cool game for your first actual finished project!
I'm also 31 and trying to do what you are doing in the spare time I have in between family, life and work.
Game is cool, addicting, simple to understand. Variety of enemies is good, posing a new challenge with each new enemy present.
I was getting quite frustrated with how small the button hitbox was. It's always best to overcompensate with hitboxes to give players extra room. Reflecting projectiles wasn't very clear to me, it took me a while to guess I was supposed to be pressing on the projectiles. Also, because there aren't that many green slimes, I wasn't really encountering having to click on the projectiles, and I also came across quite a few reflection power ups which made little sense for me.
Are you going to keep building on this, or are you moving on to something else?