The length of the game is just about perfect for a small project jam like this.
The mines are a bit underwhelming. Beat the game once before realizing there was a second feature. Would have been nice if they did more damage to the boss, and/or had a larger area of effect for the maze portion.
Part of the maze was offscreen on my monitor, but it didn't have much of a negative effect. Retry doesn't seem to work during the maze section. And I'm pretty sure the bosses attacks would multi-hit me. Would have been nice to introduce iframes, or make the attacks vanish on hit to make the bosses damage output more consistant.
I did also have a bit of a readability issue, where for a time I thought the flying error messages in the boss level were part of his attack pattern. It became a bit easier when I stopped trying to dodge them.
The maze music works, but I especially liked the music for the boss fight.
Good luck!