I saw the thumbnail and from one stealth game dev to another I knew I had to play it.
I'm not sure if it's intended or not but most of the time I can get caught and just outrun the guards which doesn't make them very scary. I think you should be able to outrun them if you do some good corner strategies and delay them behind walls and doors. but that's just a balancing issue besides that the gameplay is good maybe some more ways to distract the enemies or harder ways like throwing something etc.
Good job on the level design. it got increasingly harder with more features added, maybe add a minimap for bigger levels, especially the ones with the portal are quite confusing in the beginning.