I like the intro and first boss (didn't get past it to see more).
On the bullet hell side: it would be really helpful to have an indicator of your hitbox, I figured out that it was smaller than the player sprite, but not exactly where it was.
On the dice side: I think you could have done more with this idea. Give the other numbers different effects (e.g. healing and screen clear) or have the player be working towards a number to do damage so that low rolls will eventually hit. You still get the 'Jackpot!' feeling from a high roll, but aren't totally frustrated if you miss repeatedly.