Very challenging game!
Fought against 3 bosses (not sure how many there are in total, because I gave up at boss 3). Of these I liked the second boss the most by far (even though he took me ages to beat). For the first and third boss it was very difficult to read what was going on (I'm not used to playing this kind of game), and getting hit seemed unavoidable. In the second boss fight I felt that the explosion radius of the rockets felt a bit high (at least for the player taking full damage even when hitting the rocket was acutally just on the edge of the radius (so missing the charged shot usually meant trying to dodge the rocket until it charges again).
I played with an xbox controller which was at least somewhat easier than on the keyboard although I had to be very careful not to crouch when I wasn't intending to (so I'd suggest maybe lowering the analogue stick sensitivity for crouch?). For me it was a bit overwhelming having to learn all controls at once and I agree with the other commenter that maybe dash and jump could possibly be joined into one button.
Music and graphics are great, give the game a really nice retro feel.