I got it. Its not subtle but when I thought about it was a nice way of showing the only one theme and the title is perfect.
Only one room, only one healthbar, only one enemy.
But it would need a lot more polish, just something like getting the background to not be default blue is something that would make it a lot better.
Design 1/5
Its very little when it comes down to the gameplay.
Adherence 5/5
Got to say it was fitting well with the theme
Originality 3/5
It is very original to share your health with your enemies although the gameplay is just about getting to the door over and over again and less focused on the healthbar