This was brilliant! I loved the sound the slugs make, very satisfying.
There are a couple of things that would improve the experience like pausing when I’m placing towers, some colliders on the edges of the map so the characters don’t fall off and a larger map with more complex topography. But honestly, all that is QoL stuff that is secondary.
You’ve got a good solid gameplay loop that I can think you can expand a lot upon, just adding a full upgrade path for your weapon and the towers you can place would add a lot of variety. Maybe you can hire mercenary gnomes that parachute in, kill some slugs and then leave, different types of slugs(they’re a bit big for my liking, something smaller that explodes with an even more satisfying squish would be great!)
All in all, solid project!