This game's navigation reminds me a lot of the original Metroid. I like using the die to attack, and giving you a random bonus on the way to each switch was a neat idea. My main complaint is that the sludge monsters fire with deadly accuracy as soon as they see you. Even if you don't see it yet, you will almost immediately lose a heart once you're in its line of sight. This definitely killed me multiple times on the way to the boss.
Overall the game looks and plays quite well. Great work!