Didn't seem that difficult - BUT didn't seem that clever either.

It's simple because "reverse entropy" doesn't work. Once you understand that then you can follow the logic they present - ** AND only the logic presented is what you have to follow because it doesn't actually track.**

I think if I hadn't have read all those Greg Egan books, especially the Orthogonal trilogy I'd have been much more confused. All of the "time travel" that takes place in the book is nonsense - but it is presented as an axiom so you go with it. That's the entire point.

The explosion causing frostbite isn't reverse entropy - it's simply "OPPOSITE DAY" logic.

It's like Lisa trying to explain global warming to Homer:
Homer: Wait, wait, wait, so in August it's cold?
Lisa: That's right.
Homer: And in February, it's hot?
Lisa: Mm-hm.
Homer: So it's opposite land! Crooks chase cops, cats have puppies!
Lisa: No, Dad, it's just the weather.
Homer: So hot snow falls up?

So all my questions went away when I realized that you could have an effect without a cause and it didn't matter.

It was fine - I think of this more as a sloppy sci-fi short story rather than a mind blowing super scientifical genius movie.

Or I could be just "smart" but you have to be really really smart to "get it." Either way is fine for me.

As for the film - I watched a REMUX of the 4K discs with subtitles on and the film looked and sounded great - until the so so so overpowering final credit song - my system could not handle that.