Looper is brilliant, but not quite genius.

So I saw Looper last night and absolutely loved it. It put me in a really good mood and I was smiling when I left the cinema. There were some things in the film that I've never seen before and some really subtle scenes that will influence me in the future. I'm loving seeing Joseph Gordon-Levitt becoming the leading man I predicted he would after seeing Brick the first time. He's a great actor.

Rian Johnson is a very talented director and has a knack with writing. I liked the fact that all the characters were made a little sympathetic and the characters you expected to be rooting for did some pretty terrible things. It kept you off balance and unsure of what direction the story was taking. You're never totally sure who the hero is.

However, it did bring to mind one of my writing rules. There's something about the story that stops it just short of being a classic in spite of everything else about it being so well done.

• Always try to make your whole story develop out of the initial premise

One problem that Looper has, and I don't think I'm spoiling anything here, is the telekinesis subplot. I'm not spoiling anything as telekinesis is discussed from the very beginning of the film so it stands to reason its going to be an integral part of the film.  However, the core concept of the film is that Joseph Gordon-Levitt has to kill an older version of himself. That's very clever, he's a hitman who's facing an older and slower version of himself but who is also wiser, more experienced and has the advantage of having his memories. Brilliant.

However, the film also develops a Johnny Bravo-esque sub plot about telekinisis that actually overshadows  the main concept towards the end of the film. So you have a film that starts off being about one thing and finishes being about something else. I should say in fairness that it's all resolved very nicely and its never anything less than entertaining and clever. But there are very few films that have pulled off the trick of twisting the story into something else halfway through. Psycho maybe, The Birds, maybe Memento. You might say detective fiction has always played that trick. The gumshoe starts out investigating one thing but it turns out to be something totally different. But the main concept is that the gumshoe is investigating something. Nothing more.

Terminator is about terminators. Twelve Monkeys is about identifying who unleashed a virus in the past. Inception is about planting an idea in someone's mind and what it might do to them. They all explore a core concept and everything in them is an offshoot of that initial premise. To me that makes them neat, clean and gives them the extra oomph to lift them above the rest. Where Looper just misses the mark is in having two concepts. Its as though Johnson couldn't figure out how to make two men hunting each other for 2 hours interesting and so had to introduce another plot element to give it some legs.

We're all taught that you should be able to sum up your film in one sentence. Looper would take two.