I liked it a lot! The idea is super original and I think playing it with a friend would be very fun (I have no one to play with)
I loved the intro music and I hate you for that. Every piece of music I make sounds like shit and yet there i was, moving my head like an idiot with the rythm of the bass you made..
The drawings are very funny and the gifs made me smile. The controls are simple and responsive.
In the first level I didnt quite understood what I had to do after killing the enemies, I was waiting the level to end automatically. Maybe you could add an arrow telling me to move forward or maybe im just stupid idk. It only took me a couple of seconds to go forward though.
One or two times I tried to go to a previous menu with the Esc key and it quited the game entirely. Yes I did it more than once, and yes it was already established that im stupid. Maybe a confirmation sign before quitting?
Also I couldn't make the solo mode work. Whenever I tried to change it only the child mode changed. As I have no one to play with it was a little difficult for me to advance alone (and I refuse to use the child mode. I may be stupid and have no friends to play with but I AM NOT A CHILD). I still had a lot of fun though.
Keep it up man! Its a great game!