I enjoyed the game overall, gave me old-school doom vibes. The lighting was perfect for a horror scene. And the zombie noises were spot on. And every time I turned around and saw a zombie was quite the startle so good tick on the horror element. I also enjoyed the panic you feel when you as the payer have to enter the code before the zombies reach you, gave the game a good ticking-bomb vibe.
A few things I would love to see improved further are the bullet velocity and feedback in the gun it felt quite static when playing. Also, I had no feedback that I was getting damaged by the zombies ( other than the hp bar).
A small bug I noticed was I was unable to clear the code after an incorrect entry or it was unclear as to how I could do it.
Other than that a solid game, enjoyed it quite a lot Kudos!