Short terms: I liked it, simple in mechanic and look, but anyway it's fun and cool to watch thanks to the art style and colors chosen.

What I liked:

• Simple shapes but with small details to them that create a good-looking art style and I liked the colors that doesn't stress eyes
• Cool animations
• Really liked the mechanic of change the shooting mode ongoing whenever the player prefer it unlocked a sort of attack pattern/combo
• good variety of enemies with unique attack patterns (special honor to the one that spawn triangles)
• polished experience

My thoughts about what can be improved:

• Add sounds (not necessary a soundtrack initially)
• I've arrived at wave 15/20 normal mode (can't remember the exact number) it would be useful to have a counter at the main page showing the best run.
•  I suggest thinking a different way to permits the user to shop the power up (maybe with numbers on the keyboard?) in order to don't lose focus on shooting and aim and showing the user that we're effectively selecting a box of the power up list

I would put a 3.5 stars there are things to improve, but you've done a good job with design the art and the enemy's variety. Perfectly centered the jam theme.