Spoilers in comment for anyone who hasn't played yet I recommend doing so first!
Great premise! Your sound design was definitely great and the environmental changes had me on edge. There were a couple of scares that I missed I think because the web played didn't load them in time- and I could sort of tell when something was going to happen from the frames lagging but that's not easy to control without a lot of testing of the web build.
I think this is a fantastic idea and a decent first execution but I would love to see it pushed further. You mention being inspired by iron lung, and one of the reasons that game is so effective is because the player is actively having to navigate the world and interpret instructions, learning a new skill to do so.
I think there is a lot of potential untapped horror in giving a player a sheet of Morse code, and letting them replay a message while they decipher it. Perhaps having somewhere they are meant to input the result as well. Iron lung scares you by putting the 'jumpscare' moments in unexpected places so you aren't ready for them. But that is also a much bigger project idea and I think you've done a good job making something effective in the time given.
Things that were very effective for me were the widening and narrowing of the passage, and being unable to go up. There were several times though when I looked up of my own accord and nothing was there. I think maybe if the tapping got louder and closer sounding people might look of their own volition which would make it a more effective scare. I also think having something move the first time I look down would be good. The web effects looked great, and I loved the eerie light that appeared when it said 'its going to get dark.' the mis-match of information to reality instantly builds tension. Great work!