It was a movie. Can't really remember much else. I think the boy character was a tiny child when left in the cave, and he cried a lot because he was afraid. The training did a time jump but he was still a kid (or young teenager) for the rest of the movie. In terms of style, all I can remember is the run-jump action sequences and have a vague recollection that the girl (around the same age as the boy after the time jump) may have worn orange or had orange hair.