Modified title, just to warn people.
Oh my god, what an awesome ending.
The whole concept of applying entropy towards wish making is pretty damn cool (Change in entropy is always greater than or equal to 0; change in despair vs. hope is always greater than or equal to 0).
One little complaint: the universe isn’t running out of energy. Energy simply tends to change to less and less usable forms. Of course, this is based on a classical understanding of energy, so that’s probably going to change in the future.