[Spoilers] Can I ask what the black shape was that you could catch a glimpse of near the end of Supermarket? I didn't get a clear look but boy, did that scare the bejeebus out of me when I saw it. Full body flinch and everything
In the code of the game, it's called the Skitter. It shows up about halfway through and attaches itself to your back. By running or turning quickly, you can catch a glimpse of it, but you can never escape it. It feeds back into the core idea of the game: that there's something behind you, and there's nothing you can do about it.