Great game and very, VERY creative idea! If I had to categorize this game I'd add it into the SPOILERS...
Bullet Hell genre but the fact that it's main gameplay loop is that of a casual game is so interesting, unique, and most importantly, very fun!! I loved the dialogue and charming nature of the characters and really love the way the backgrounds and art is done! It's all such a unique, yet familiar feeling like those nostalgic flash games! A couple of critiques/suggestions. I'd consider adding a rank system, or some type of system that changes the amount of money gained after each level. This way, impactful gameplay such as taking no damage, beating a level in a certain amount of time, cleaning all the teeth before they grow wings ect. can be rewarded. The minimum amount of money per level is fine, but a system like this can add more towards the entire upgrade system. A skip text button would also be nice for those that may want to replay the game or speedrun it. This may be a purposeful choice, but I feel that the invincibility window after getting hit is a little short, and think that extending it, just a little bit, would allow for more freedom of gameplay especially during the last enemy chase scenes. They can shoot out a barrage of constant attacks, and since you have to get really close to attack, you're very prone to getting hit multiple times. That's pretty much it for my problems with the game, I'm super interested in this and seeing how it'll turn out! You really did an amazing job and I can't wait to see how far it comes! :)