Changes may have the most creative story from IFComp 2012: you wake up in the body of a rabbit, but with the mind of a human. This isn't some "intelligent rabbit" or Watership Down thing, here. You're on a person-free planet called Elysia. And you observe how you became a rabbit: animals are putting other animals into the same sort of pod you came out of, and they are switching bodies. They know this instinctively. So your main task is: how do I find what happened to my body?
I remember almost giving up on Changes because the start was unclear and hostile and even random. You had a very diligent fox chasing you around, and being able to sense animal emotions around you only did so much--if the fox wanted to play prevent defense randomly, gosh darn it, it would, until you got impatient, and only trial and error showed where you were safe (Oddly, you could also run past the fox if, say, you were south of it, it chased, and you went north. Hooray for mimesis and feeling fear?) It wasn't really clear what animal you'd want to become, as everyone else was bigger than you. The solution wasn't that clear to me, though it seems hinted in retrospect. Along the way I found a ton of insta-deaths. There was one place where I fell into a lake and drowned, because rabbits couldn't swim.
This is the big clue here, because you need to become something that can swim, and there's only one real animal that can. I didn't find it at all obvious how to kill them, though in retrospect, it makes sense. I guess the solution felt like something you'd see in a cartoon, and not a serious sci-fi work. But once I took the new animal's body, I saw more of what to do.
I did not drown in the lake, but my predator did. Then I managed to annoy another animal and kill them. There were deer to manipulate and avoid. I noticed an abandoned shuttle which, well, looked familiar. I needed to become an animal that had something resembling fingers--all through the game, I spent time dragging the bodies of animals I'd killed by their teeth, into the cocoon and then out.
Opening the space shuttle is the big thing, and while actually moving a human body back to near the pod (there's no animal big enough to carry the body) again feels a bit cartoonish to envision, it's pretty much "do what you can to cause a disturbance."
Nevertheless it's all very clever to watch and see unfold, and each time you change animal skins, you get a flashback detailing more of the story. Perhaps you'll be able to guess it sooner than I did. But even escaping in human form doesn't change anything. There's a mythical feel to Changes, including the ending, which is far from "you board the shuttle and race home, vowing never to get near Elysia again." There's a tale of human tragedy and conflict to unravel, and the feeling I had that I was disturbing something perfect and special was, in fact, validated by the end.
Some parts of Changes do feel a bit loose, and they stop it from soaring. There seem to be more locations than necessary, and chasing certain enemy animals gets exhausting. But the payoff is legitimately rewarding, and with Andromeda Apocalypse won the IFComp that year, I can't help but thing Changes would've had a shot with a good deal more polish.
As-is, I remember the author had a bug tracker with a lot fixed, and there were obviously a lot of different moving parts with several animal NPCs. They all act pretty simply, with beavers hissing or deer fleeing, but they build a world remarkably quickly with little need for detailed scenery. As someone who is indulgent about using walkthroughs and giving the author a mulligan for a puzzle or two that may be a logical jump too far, I really enjoyed Changes, even though the random events and NPCs bouncing around made it hard to execute. Perhaps it added to the feel that I, as (initially) a human, had trespassed somewhere I should not have been, in the name of progress. It combines eerie naturalism with sci-fi horror in a way I don't recall any other IFComp games doing.