This one is tough for me to critique- for what it is and the time it was made in, this is pretty good! There are certainly some issues with it, but as you were working solo it's hard for me to really fault you. I don't know if you plan on updating the game, but below I'll mention some suggestions if you were to do so:
As it stands, there is very little telegraphing. Eventually I realized the main premise- that the dice affects the attack pattern being used- but this makes me wonder why the boss isn't itself the dice. I think this would help make it much more obvious that the two are related, and as an added bonus, you wouldn't need the dice UI taking up the corner of the screen.
The general difficulty of the different attacks seems quite unbalanced. Several of them seem to be very unpredictable, while others have very obvious telegraphing that makes them easier to play around (such as the meteors). I suspect that you planned on doing more stuff to help with this but simply ran out of time though- I know all to well what that is like, including in the game I worked on this jam 😂
The graphics are simple but serviceable and feel intentionally minimalistic, which I think works well for what this is. Anyhow, nice entry!