In his intoxicating new film , takes us on a dreamlike journey through the doomed relationship of a young pair of self-centred lovers. We caught up with him in New York to discuss romance, parallel universes and `s fantastic Marty McFly impression…

Did you enjoy making the film?

I loved the making the film, it was such an intimate film to make because it was really me and the two actors, and we spent so much time rehearsing which is unheard of on an independent film. We actually went to Justin`s cabin up in Massachusetts and spent the whole weekend there just going through the script, going through all the scenes, rehearsing and figuring out all the beats. It was unlike any rehearsals I`ve had, because there`s usually no time to do anything remotely close to that; it`s always just having the actors figure it out on the day, and because the film is just focused on these two people, it had an intimate feeling that you don’t really get on other productions.

Because of course, aside from the two partners at the beginning, the action revolves around just these two characters…

Yeah, at the beginning, there`s Eric Winter who plays Kimberly ()`s boyfriend, and then Kayla (Servi), who`s awesome, who Dell (Justin Long) is with in the opening scene, but aside from those two, the film is basically just Dell and Kimberly. Justin is incredibly quick and smart and funny. We were doing a lot of night shoots in Hollywood Forever Cemetery, so everybody was tired; it`s tough on the system! But I remember one time the sun was coming up and Justin was cracking jokes. He does this amazing impersonation of Marty McFly from Back to the Future, just keeping everyone`s spirits up.

So with the two playing through this doomed relationship, how did they get on on-set?

Well, Justin and Emmy were actually friends before the movie. In fact that was the reason why Justin read the script; Emmy had Justin come to me and I was also a fan so of course I said absolutely! Emmy sent him the script one day and then I got the call saying he wanted to do it, and he was basically in the film the next day!

Comet is a film that manages to turn every romantic cliché on its head; you jump around in the relationship so much. Why did you decide to go with its disjointed narrative rather than the straight narrative you would normally get in a romantic film?

Basically I wanted to do a break-up movie. I wanted to do a movie about heartbreak, because I actually find that`s way more universal than happily ever after, which is what most romantic comedies tend to be. So I was thinking about what the emotions are when you break up with someone, especially when it`s a long relationship and you`re in love with that person. What does that feel like? From my experience, you just start remembering different details, the good times and the bad times, and they just start to flood over you. That`s where I came up with the structure of Comet. I`d written it as five love scenes, each exploring a seminal moment of the relationship, but it didn’t feel cinematic at all. But then I went through a big break-up myself and I started having these moments of the relationship flash back, some happy some sad, which gave me the idea for the final structure of Comet.

Why did you choose this idea of parallel universes?

Because I think that has a lot to do with relationships. That’s what people think about when things go wrong, especially when there`s a break-up. You go back over and over “if I had done this differently, if I`d not said that at that time, or I had taken her on that trip, or if I`d met her before that guy, or if she had never met that guy.” You play the What If Game so much when you`re going through a break-up and that exploration is what I really wanted the movie to focus on; this guy who`s so into trying to rationalize logically why this person should be with him that he misses the point. It makes him distanced from the love of his life, and eventually makes him lose the love of his life, so I think that to me it`s a thematic thing of when you`re in a relationship, the questions that you ask yourself. It also gave me the creative license to do some interesting things visually. I wanted to externalize their emotions visually and so I put up this idea of going a few parallel universes over and that gave me the license to do some of those things. I wanted this abstract depiction of what Dell is feeling and going through. Of how he remembers things, or doesn`t. Is he dreaming, or is this real? There`s pieces of reality mixed in with pieces of dreams. I wanted it to feel like a painting, which is one of the things that Kimberly talks about, with everything blending together. Although we jump around, it just helps to tie everything together visually.

The idea of lying throughout a relationship features strongly in the film, so when we come to the end of the movie, we find ourselves wondering how much is actually true between the protagonists. How much do you see as the truth between them?

(laughing) In one parallel universe things are true, and in another, they`re a lie. To me, everything is up to the audience. You can choose which path you want the characters to go on. The idea of parallel worlds means there are multiple versions of what ends up happening to Dell and Kimberly, so it really is up to you depending on what view you want to take. But all those different endings I believe do happen, and I think that by the end of the film it doesn’t matter which way you want to go, because the journey ends with Dell finally accepting the fact that love is real. That for me is where the story ends.

Comet is in cinemas 3 July 2015