Fun, but frustrating. I had a good time playing this (though hard mode was basically impossible for my 5 centimetres cubed of brain). The main things I would say it that the hitboxes aren't perfect when in terms of getting the timing right, and the attack doesn't feel quick enough and hence not responsive enough. In terms of sound, the music track was good and totally fit the tone and atmosphere, but didn't feel melodic or rhythmic enough for a rhythm game like this. As well with sound, I'd say it would heavily benefit from more punchy sound effects - to really emphasise the whole "swing on the beat" and it would really mark out the rhythm. The sound effect you used is more of a soft "whoosh" sound, which blends in quite a lot with the music. For a rhythm game you really want to show how you are hitting to the rhythm, and punchy sounds normally help that. Overall, really good job and well done on the game!