A great start for a platformer, there are a few things to consider the first is Graphics consistancy, throughout this demo your players pixels are unfiltered as well as enemies but some of the tiles for the castle were bilinear filtered which is quite jarring against the crisp pixel based tiles this made some of the areas look blurry, the boss of this level was far easier than the smaller enemy counterparts in the level i believe this is to do with the boss being so big and its attack check being small perhaps adding obstables to the fight or giving the boss multiple phases could aleviate this and make this a satisfying final battle
overall your use of combo skills makes the player feel good in fights and overall the enemies are pretty satisfying to fight