SOLVED. Old science fiction story of kids trapped in a machine. [s]

[Pablo]

I read, but didn't quite finish, this old story about a group of five or six teenagers living in a world controlled by some A.I. machine that manipulated every aspect of the virtual reality for its own amusement. The machine, I think they called it "IT", threw blizzards and caves and the like at the group, maybe one lost a leg, Simon maybe was his name? I'm surprisingly fuzzy on it, considering I probably read it in late 2015. It was just text on some web page, but transcribed from a regular old book or anthology written maybe in the sixties or seventies--awfully prescient, I guess, but not out of the question considering what Orwell was writing in the forties. If I had to guess, the author may have been Bradbury, as looking through my search history revealed that I read a PDF of The Veldt in September 2015, but I also read The Library of Babel by Jorge Borges online a month later in my history. Some digging around on Wikipedia made me suspect something out of Bradbury's The Illustrated Man, but none of the titles in the table of contents rung a bell.
The group of kids seemed to be in eternal torture for IT's pleasure, just as I'm now burning to remember anything else about it. Maybe the computer's name was slightly different, like IM or M. I'm pretty sure that it was very short and in all caps, though. The book was in relatively short sections, marked chronologically, almost like the group (or one character's) log or diary. They centered headings with maybe the day and month, or just a day number (like 312) or it could have just been by year. The group seemed to be wandering along some destined direction, and with some internal strife that mainly resolved with the main dude, or maybe the second-sanest/in-charge person, who I think was a girl.
Anyway, I wanted to go back and finish it, but I have no idea what it was called, and it didn't seem to show up in my search history near The Veldt (which, although similar, is not this book), so I'd love any help you all can muster!

[Nóinín]

In Harlan Ellison's short story “I Have No Mouth, and I Must Scream“ five humans, assumedly earth's last survivors, are trapped inside a computer called 'AM'. The computer keeps them alive and tortures them to exact its revenge on humankind. They are not children, though, and there are no individual chapters. Maybe your story was based on that one? You might try a “similar to...“ search.

[Pablo]

Nóinín wrote: "In Harlan Ellison's short story “I Have No Mouth, and I Must Scream“ five humans, assumedly earth's last survivors, are trapped inside a comp..."
I think that was it, actually! Thanks so much. And the opening image of a hanging, drained corpse is actually pretty familiar. Also, the day of the week is pretty regularly mentioned, and they say it's the 109th year inside, so I think that's why I remembered time headings. Above all, a computer called AM is too similar to be a coincidence.