Thanks for the feedback!
For the upgrades part -> there are more upgrades than only the hands, health, and damage. There is an upgrade that charges up based on how long you can hold the bass in the music, and then you can press "e" to release a big explosion. Additionally, also a shield that makes damages to enemies based on the current volume of the music. There are some more "small" upgrades. Also, you can have a total of 3 hands that will fight for you. I would've loved to implement more, but upgrades cost a lot of time :/
For the auto attack and boss part -> I totally agree with you, and I had it on my list, but I was too late to implement it.