I can't remember the title to a French (I think) film about two children (a boy and a girl) who were best friends growing up. They had a game they played with a jack-in-the-box (I think, or it could have been a small ball) where whoever had the object had to do something outragous (essentially a dare). As they grew older, the dares got more daring (so to speak). Also, they grew apart at some point, but were brought back together because of their true love for each other.
Does this sound famililar to anyone?