Very well done! Good controls, great graphics, fitting music.
I instinctively try to avoid the red HP pickups (because red is the color of enemy shots), so maybe change colors a bit.
The idea is good, so if you improve this further it would be cool with some bigger changes from the dice, not just percentage buffs. Maybe different weapons, elemental attacks, enemies now explode when they die, critical hits, stuff like that. Add some long-term progression, and you have a great game! :)