Very nice fight, although I would bring a few corrections
- That blue laser attack comes without any warning or indicator, it feels extremely weird and unfair, completely breaking the rythm of the fight, but as far as I went that's the only attack that felt a bit weird
-Also, when you move against a side of the "box" (for example bottom side) by pressing two keys that make a diagonal direction (for example left and down) you go much faster than when you move normally, which I do not think is intended?
besides that, although the boss design is very basic and the music repetitive, I like what you did with it a lot, the score might be a bit harsh but it is only because the game is, despite it's good points, a single boss fight, so it is hard to rate it much higher
Keep it up though, it was a nice work!