Thanks for your review, I'm glad you generally enjoyed my game! That you like my art and the sounds I've cobbled together feels great, I'm a programmer first, and only dabbled a bit with 16 bit pixel art i my youth :-)
The physic system is largely inherited from this general sub-genre of game, starting with Boulder Dash. It is generally completely deterministic (a boulder dropped on top of another one will always fall to the left, unless that side is currently blocked) as is fitting for a puzzle game, but it's true that it can be counter-intuitive, as is probably inevitable with all grid-based physics. My hope is that people will learn as they play, and that I can introduce it in a way that it never feels too frustrating.
As for "Explosive", well, the odd looking wall can be destroyed, and the monster can help... :-)