Cool game. I liked how fast and smooth it plays when you slide, wall jump and wall run. Especially that last part before the boss where you get to wall run and wall jump a lot was very satisfying.
Having the miniboss so late on the stage with no heals felt a bit unfair and frustrating, especially if you get hurt early on you're incentivized to kill yourself just so you can maximize your chances on the miniboss. Maybe a partial heal of 2-3 bars before it would be fair?
As for the last boss I think it had just the right difficulty where it took multiple attempts without feeling frustrating. I just didn't like that his body hurt you, especially when he's clearly in recovery frames with his sword down. At some points it becomes very ambiguous if you can slide under the wall attack which felt a little unfair when you fail to slide under him but it was no big deal. Might want to give the player full health when he enters the boss room for the first time.
I played on an xbox 360 controller and I could be the only one thinking this but I would have prefered to use the analogue stick for movement instead of the d-pad because my thumb becomes sore when using the d-pad long durations. Also usually A is the affirmative button in menus and not X.