Timing was off
I'm a musician, and the one thing that can ruin these type of games more than anything is when the timing is off from the music. The first couple were ok, although not exact. The third one though was way off. I'd be hitting the correct key at the same exact moment as the note was played, and it would tell me I missed and I would start getting a negative combo. I can tell you, it isn't much fun after that.
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