Explaining the bad reviews
Those users rating badly kind of have a point, but it is overly exaggerated.
The graphics could use a little work, and you could make the game a lot longer (like adding multiple levels or more boss fights) but that's about it. They're just over-exaggerating because they can't beat the game. It's a very decent game, and personally, I think the level of difficulty is perfect. It's hard at first, but then you get used to it and it becomes much easier. If you make a sequal, then you should definatley add in mroe levels, as I have already stated, and level up features. If you decide to make the whole game just bosses, then you level up after each boss. If you add proper levels, then obviously, use expierience points. And try to improve on your graphics a little bit.
Overall, a nice little game, and you get a solid 9 for it!