Admittedly I don't play very many mouse avoider games, but this one caught my eye. There were only two complaints I had. One was the shaking of the dialog box at specific levels made me have to strain to read them, I understand this is likely for situational effect, but it is something to think about. The other is that on the BBEG, it is possible to easily defeat by simply parking yourself right in front of the weak spot, taking only a couple hits from the cannons and only needing to move once the central beam fires.
Other than that, the game is quite fun; not too long, not too short, the music fit pretty well. I liked the simple, but elegant story. I'd say your experiment of make a mouse avoider with story was a solid success. Keep up the good work.