My thoughts:
Static builds up too little, compared to what it takes to kill you. It's quite jarring for Slender Man to catch you while there is barely any static on screen. The audio should also get increasingly distorted the longer you look.
It seems a bit unfair to have him move towards you while you look at him. Part of the ingenuity of Slender games is that he doesn't move while you look at him, but looking for too long kills you. He also doesn't have a walking animation, which makes him look very silly as he slides across the ground.
I feel the atmosphere isn't scary enough. It's a bit too bright, and the music isn't unsettling enough. There are also no good scares. A little jumpscare sound when he gets close would be nice.
The Slender Man model doesn't look particularly threatening, it's a bit too small. I also feel like this particular model (from Slender: The Arrival) has been way too overused in Slender games by now, perhaps there's a better model out there that you can use?
The game overall needs more optimisation. It's a pretty small and short experience, so it really shouldn't have to take up a full gigabyte of space. (For comparison, the original Slender: The Eight Pages was 118 MB in size)
Overall this is a good starting point, but needs work.