Are you sitting comfortably? Are you a tolerant, open-minded person reading this? How about if someone walks into your house, your bathroom, while your daughter is taking a shower. They act extremely weird. Can you still be kind and tolerant, acting reasonably towards a strapping young man who, unknown to you, is autistic?

The tagline for this film is, "Normality is relative." So just how much of someone else's normality can you take?

According to director Elissa Down, the Black Balloon is, "a metaphor for a 'different' childhood filled with moments of chaos, joy and sadness for what may have been." Our cinematic awareness of autism is probably defined by Rain Man, or the more nuanced but rarely seen Snow Cake. Elissa Down says how, "it was very important in the rehearsal process to take it to the streets and for Thomas and Charlie and Jackie and Thomas to do some road-testing of their characters in public." Charlie, her main character, announces the family arrival to the neighbours by banging a wooden spoon and wailing on the front lawn. Charlie doesn't speak. He's autistic and has ADD. He's unpredictable, unmanageable, and often disgusting. He recalls not the mediated autism of Rain Man or Snow Flake but the out-of-control weirdness appropriated by Lars von Trier's characters in the controversial film, The Idiots.

Charlie is not 'nice' – at least not until you've managed to see him through the eyes of his devoted parents. To them, he is like a big child who has frequent tantrums. He's not an ideal brother to younger sibling Thomas, who's just turning sixteen. Especially as the girl in the shower is the girl he is trying to date. Especially as when he finally has her over to dinner, Charlie gets his testosterone-filled kit out at the table and gives it a good rub.

The shower girl is Jackie Masters, Thomas' partner for basic life-saving classes at school. In what seems like a happy nod to mainstream cinema, Jackie is not only gorgeous but has a beautiful personality. She helps Thomas to feel more caring towards his brother as they soon form a threesome for days out together.

Toni Collette plays the boys' Mum, heavily pregnant. Which means Charlie is called on to help Dad around the house a bit more and with looking after Thomas.

The Black Balloon is an excellent example of Australian cinemas coming-of-age movies. It fearlessly reaches outside the box and sets up a tug-of-war between normalcy and idiosyncrasy. Although there are elements of rather unsubtle box-office pandering (the photogenic young couple and a rather simplistic finale) it opens up new challenges in the way we think about people. The Black Balloon is a film of which to be proud.