I think the prose of this could use some tweaking. I guess it’s realistic in the aspect that it seems like a letter someone would write, but it doesn’t flow as nicely as I think it could. The structure was very obviously trying to mimic the standard level template, and I feel like you could’ve blended it in with the rest of the letter a bit more. It kind of broke the immersion for me.
I do like the ending, as Endrew said, the hints of obsession were there, but I feel like you could’ve just done more with it, you know? It feels more comedic than it is scary, and maybe that was your goal, but I think that hinders the story more than it elevates it.
I will say that the letter thing was pretty cool. I do like all the different coding elements that tie this all together (I’m sure looking back you have your own issues with it, but I think it’s still pretty neat.)
Overall, I like this, but I feel like there’s a bit too much holding it back for me to upvote it.