here is my demo (first run)
For a first map the brushwork and lighting is really nice.
The path of the player is sometimes confuse but it's ok you know where you need to go.
Adding a void, space or cloud skybox could be cool on this map.
I'm not a good player so I play in skill 1
I couldn't finish the map the end is too hard :
You put a shambler and a huge green shambler in a room where you can't hide with other enemies around, It was impossible to survive the end for me. (I'm waiting for others demo to compare :D)
I didn't understand how to get the yellow key.
I did a rocket jump to take it but I'm pretty sure that's not the good way.
Anyway the rest of the gameplay is good, even if I hate platforms. (it's stressing me so much when i'm recording a first playing demo).
Great job for the rest. I'll watch for your next stuff !