A really polished prototype for a platformer with good spritework and animations.
In my opinion, this game lacks of some reward system. You should reward player for his actions, like killing and beating the level.
And as the game is skill-based I'd advice to reward player for doing good in your game, so there will be much more motivation to master your game.
Also as your game feels exactly like Ninja Gaiden I suggest you to read my review I wrote for NightmareDemonCastle. It has a recommendation that I would also recommend to you, to make a some unique gimmick that will make your game distinct from similar genre representatives.