gonna guess you're baking in the shadows...? How does it handle the voxels though?
would be nice if they weren't so dark though. but it seems like according to your post you are able to modify that.
It's actually taking the sprite model and compressing it then projecting it on a plane, then using opengl tricks to only render on the right surfaces. 
Since the game mainly consists of a few different tile types I can do this with relatively low impact and draw calls. I'm thinking of making it project onto walls and a few other surfaces as well, there will be various quality options in case this ends up impacting performance. 
Though sadly this means nothing fancy like self shadowing, or projecting shadows onto other sprites :(
The plan is to make them fainter and blend, just have to get the settings right.
So did we reach the shader stretch goal??
No, I just got really sidetracked. I just kept reading random bits of how people did certain rendering tricks and was like "hey I can do that", so then I did.
it looks kind of weird for the objects to cast shadows like that (regardless of actual lighting) and the walls not to; imo it'd be better if they just casted a diffuse shadow straight down
I can make this an option, but once I'm done it'll look great.
Plus you can't imagine how many AAA games have completely forgeted shadows that make no sense. When doing all this stuff I compared with various game images while trying to figure out the "realest" way to do things, turns out a lot of games just fake everything.
Also some walls are going to cast shadows. Just need to figure out a balance between what looks good, and what breaks your mind trying to figure out how the dungeon is actually structured.
Is Dungeon Master Mode still a possibility even though the stretch goal wasn't met? It was a great idea and I feel that would set this game apart from any other co-op rouge-like game.
Not sure but I hope eventually, would happen after release.
Edit: one more random preview pic

Edit2: Oh my I just realized the falling floor tiles are reflecting into the real world o.O