The filmmaker insisted on actually filming the stunts without the use of green screen or visual effects and instead he asked leading man Michael Fassbender and the film's stunt experts to show off what's humanly possible.

"We got together an Olympian group of stuntmen, who were dying to do something like this because they never get the chance now, because they're always on set in front of green screens hooking actors up," Kerzel explains. "To actually get them to it and see what was achievable was very exciting to us."

And there was one stunt that still leaves the director speechless.

"It was probably the biggest stunt," he tells WENN. "It was this 120 foot leap of faith (from one building to another) that (stuntman) Damien Walters did, which was the biggest that's been attempted in the last 30 years on set.

"It's pretty remarkable when you see people go to those physical extremes and you're capturing it on film. That was important to not just have a CG (computer-generated) character which came from the spirit of the game."