It's been over 10 years since I've seen it. Tho I do remember enough of it to give it an honest rating, I would definitely like to see this again!
Rafal Zielinski dug a lot inside the psychological nature of born killer as it was a manner to express themselves in, via these two teenagers, we cannot trust what they said about themselves, or the torture and rape they might suffer with their families, because they didn't have the disconnection dissociation between realities and fictions, but we can feel how much they were in need for love, fun, happiness and personality.
Good metal music and editing, love the way of telling the event with flashback. It's fun to watch it, though the irony is it's a murder for fun!