This is a really fun idea! Music and art are great too. You definitely weren't lying about it being difficult though lol. I'd be more willing to keep attempting the second phase of the boss if the first phase didn't take like 10 hits to get through.
The controls feel a little clunky though, there were a lot of times where I'd be charging a jump, start moving in a direction, then lose my jump since I released space bar just as I was walking off a ledge (A few frames of coyote time would help a lot I think).
Overall, great job!