Margot Robbie felt there was a different kind of energy on set for Birds Of Prey. Firstly, it was a young set, run by a lot of women.
"But it also had a bit of an indie spirit, I think," muses the Aussie actress (29), who plays lead character Harley Quinn (and is producing the film via her very own production company, LuckyChap).
"It is a much smaller budget than comic-book films normally are, because it's R-rated, so there was very much that collaborative atmosphere and 'roll up your sleeves, get down and dirty and just get the job done'. And have fun while doing it, which - when it's a big production value kind of set - sometimes you miss that. You feel like you're in a bit of a machine."
And Robbie, who first found fame in soap Neighbours, has had plenty of experience on Hollywood sets over the last few years.
Just to name a few of her projects, there's been drama I, Tonya (for which she gained an Oscar nomination for Best Actress), Quentin Tarantino epic Once Upon A Time in... Hollywood, and a superhero film in the shape of 2016's Suicide Squad, in which she played the villainous Harley.
In Birds of Prey, the DC Comics Universe character - who first appeared in Batman: The Animated Series in September 1992 - gets her very own story.
She's on the run, unprotected, and with every thug in Gotham running after her, including crime lord Roman Sionis (Ewan McGregor).
Meanwhile, Roman and his zealous right-hand Victor Zsasz (Chris Messina) put a target on a young girl named Cass and the city is turned upside down looking for her.
When Harley's path collides with Huntress (Mary Elizabeth Winstead), Black Canary (Jurnee Smollett-Bell) and Renee Montoya (Rosie Perez), the unlikely foursome decide to team up to take Roman down.
"We were shooting in downtown LA... It really represents a different side of Gotham, because we're street level, we're in the gutters, we're in alleyways," notes Robbie, who's married to British film director Tom Ackerley (they first met when working on 2013 film Suite Francaise).
"It's not Bruce Wayne's Gotham, it's not on a rooftop or high-rise in a Manhattan version of Gotham. It's not shiny, but it is colourful. It's very pulpy, kinda like Eighties mural, with a lot of graffiti."
The female gaze on this film is notable. It was written by Christina Hodson, directed by Cathy Yan, and there were female producers (including Robbie) involved.
It was something New Yorker Smollett-Bell found refreshing.
"There are so many women behind the camera and in front of the camera, so we were able to ask questions like, 'Well, what do we think is tough?' Or, 'What do we think is sexy?'" suggests the 33-year-old star, known for her Emmy Award-winning TV series Friday Night Lights.
"There were parts where you were like, 'Oh this is different!' - that is true. I'm used to being one of the only women in the cast. We had such a girl gang, such a support team with each other."
Black Canary - real name Dinah Lance - is the only one in the Birds of Prey group who has a proper superpower; her killer voice, the signature 'canary cry'.
"One of the things that I love about Dinah is her heart - she's all heart," Smollett-Bell says of her character.
"She's all compassion. She's also this amazing martial artist and expert street fighter, however, when we meet her in the film, she hasn't yet become this powerful Black Canary that we know her to be, she hasn't really owned her strength or power."
The action-packed film begins with an explosive break-up: Harley is no longer with her one true love, the Joker.
As Robbie puts it: "Though she'll tell you it was her choice and that she's handling it really well, you can see that it very much wasn't, which is the classic unreliable narrator aspect of her that Christina Hodson and I so enjoyed playing with."
It's interesting how in the rest of the movie, there's a real absence of relationships with men.
"Hey, I love love stories," says Robbie, when asked how important that was to show on screen. "But in Harley's case, if you're going to have The Joker, it's so all-consuming, there's not going to be room for much else.
"And so, it was a conscious decision to begin with, not to include that relationship as the driving narrative, because there was so many other interesting things we wanted to explore. And it's kinda all or nothing with him, so he gets the boot at the beginning."
The charismatic star - who can also be seen in Bombshell in cinemas currently - founded LuckyChap Entertainment with Ackerley, Josey McNamara and Sophia Kerr back in 2014.
She explains how Birds of Prey fitted the ethos of the company.
"First and foremost, we love stories, we love telling stories, we love compelling characters.
"I think we naturally gravitate towards female-driven content because a) there's a lack of it and we feel a responsibility to attack the statistics in the industry. But b) that's really where our interest lies. There's a gap in the market - an opportunity - something like an R-rated girl-gang action film hasn't been done."
It's certainly a girl gang to be reckoned with.
"I wanted to see what Harley would be like without someone to take care of her," Robbie elaborates on the ideas behind the film.
"And it's always been a part of my own life to have a group of girlfriends that do everything together. We're a very mixed bag of personalities, but everyone loves each other despite being pretty different.
"That's what drew me to developing a story for Harley with the Birds of Prey, to find a group that's unique, but who complement each other, especially in their fighting styles. Together, they make up all the pieces of the puzzle."
Birds Of Prey is in cinemas now