I love the idea, the problem is the inconsistence of the shadow rendering the game way too hard and frustrating.
Space to switch with the shadows felt really unfamiliar for me since it's more commun to have space for jump (my opinion) I still love playing through the level but would be better if the shadows worked more properly. (i also totally not played with the dash, i tried again and it doesn't really feel good to use, it make passing gap easier for sure but still feel a bit off. I think it's tied to velocity so sometimes it propulse hard, other time not enough)
Last, sometimes when we touch the lava it only slow the game so sometimes we can't tell if we are going to live or not, i die one time without understanding why (i only assume it's the lava but not sure) some particle or something would be great.
I also found an exploit that allow to cheese all level, you can in fact erase the ceilling when the shadow bump it's head against it. It allow the player to reach easily above the level and just going anywhere he want by jumping down to fetch key or stuff.
The game felt too hard from the start but it's a good game concept that need more polish. It's a great game !