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First and foremost, nice game. I've been missing games of this genre. Very nice settings and character design also. However, there are some things that really need your attention before this game becomes a 5/5, imo:
The screen height movement is too limited (we get hit many times just for lack of space to dodge to), it almost feels like 2d atari fighting games in this sense (there's only jump in some cases, and sometimes not even that protects you). Also, although the gameplay is quite smooth, it could feature combos (a different attack when attacking during dash or a grab move when too close) in order to avoid symple button mashing (necessary to keep the game interesting when more levels are added s movement is over, specially against the boss.
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I agree with other commentators and I just have one thing to add : OMG such great musics !!! I don't know if they come from somewhere else or if you created them, but for me it's the best thing in the game :D. I even recorded them with wavepad in its free version.