As a proof of concept/demo, this is very good. The style is very cohesive, the music and audio match well, and the instructions were laid out in a very easy to understand way. Unfortunately, the game is too hard. I cannot get past level three, and I have tried 15 times. The enemies get too strong too quickly- the block transversal is too expensive, as even starting at 50 means you can only move 30 tiles max, total, by level 3.
I would balance this by having block transversal have a CHANCE at decreasing soul, and maybe only making the enemies increase by 1 dmg each level. In fact, scratch that: I would change this entirely to remove the random decrease amounts and turn it strategy: you get this amount of soul per level, each death resets that current level, and a certain amount of deaths until you get sent back to level one. Basically, an import goal here is to decrease player frustration and make the game possible to win.