Here's some feedback on your game:
1. Theme
I like the concept of having a building phase and then a phase where the enemies come, and also that you step-by-step have to level up.
2. Gameplay
That said, while the gameplay is definetly addicting, there are some huuuuugggeee balancing issues: After just a few runs you only place the giant blasters and the other optinos are basically useless. Also, there isn't much strategy involved - just place as much stuff as possible. I would have liked a upgrading system with weapons that have upsides and downsides better.
3. Graphics
The graphics are actually really well made, but context matters! The background looks a bit empty and also - a better color scheme would improve the graphics a lot! I can recommend sites like Coolors.co.
4. Sound
The sounds aren't that bad, but they just are too loud and too many when too many weapons are placed. The music is also okay, but a bit generic.
I hope my feedback helped you, we also made a tower-defense game, so maybe check that out if you have time. Thanks! :)