Make it better.
The gameplay was excellent, but way too simple. I loved the different types of enemies and the way that your sword marked the air, but it just wasn't challenging enough. You should totally just make a new one with platforms, different combat techniques (different combos, different attacks even if its just STAB and SLASH, you know.), multiple bosses, maybe a storyline. This game has excellent potential, but yer just not using it. Look at games like Ninjaman with great combos. Also, weapons like shaolin spades and katanas and other ninja/samurai weapons to pick up would be cool. If you did this, you would have made the best game ever.