Lighting doesn't make much sense, as the shadows are not consistent.

I've made this gif for you to illustrate how I work out where to put shadows:



Some consistent rules will help tie things together. Lit vs unlit planes don't have much contrast atm, but also lit horizontal vs lit vertical planes could do with more contrast too (besides the stairs).  Don't quite understand how you're deciding which edges to black-outline, but doesn't appear consistent at first glance. 

The projection isn't even so consistent. Stairs are sort of weird because they have no depth (should start further down).  Walls are somehow higher when you've traveled Z-wards (should be shorter or have a transition). [This one's not so noticeable, I often ignore it, but it helps to sort of think of it all dimensionally].

Prefer the limited palette too - only real loss is the stubble-grey, for me.

their choice of colors is tacky

That was so amusingly unnecessary.

Finally I know what everyone's talking about - today I perceive it completely as blue + black too.  Very interesting optical illusion.  Yesterday I was all grumpy thinking everyone is crazy for not seeing it as if it's white and gold.