WARNING! This story contains spoilers about the novel Ready Player One and its film adaptation from Steven Spielberg.

With Ready Player One finally out in theaters, there are probably plenty of real-world Gunters looking for all the Easter eggs director Steve Spielberg was able to cram into his cinematic adaptation of Ernest Cline's novel. Some are obvious and mainstream like the Iron Giant, T-rex, and Doc Brown's DeLorean, while others are a tad more obscure and idiosyncratic like Madballs and Warren Robinett hiding the first-ever Easter egg in Adventure for the Atari 2600. Whether you're a pop culture zealot or not, there's a little something for everyone in Ready Player One, a love letter to the '80s and beyond.

But just when you think you've spotted all the surprises baked into the film, along comes The Art of Ready Player One, from Insight Editions. Written by veteran film journalist Gina McIntyre, the book contains a foreword by Spielberg, an introduction by Cline, and plenty of designs and behind-the-scenes stories from the cast and crew. As Cline says, this tome is akin to the "Grail Diary" that Wade Watts has in the novel, a concept borrowed from Indiana Jones and The Last Crusade. You know, the one Hitler autographed at the Nazi book-burning scene.

We got our hands on a preview copy of the book (out April 17) and mined it for stuff you just can't get out of the movie. Below are seven revelations about the making of Ready Player One that scored the highest with us.

It is Spielberg's most challenging movie to date

In his foreword, the legendary director describes the movie as "one of the most challenging films I would ever direct. And it was, taking almost three years to bring to life." With a mix of extensive CGI and live-action elements, the process, Spielberg says, was almost like making two movies at once. In fact, the first six weeks of production were entirely focused on the virtual scenes, taking place on a motion-capture sound stage called the "volume."

While putting together the final showdown on Planet Doom, the folks at ILM had to write a program from scratch to make the sequence work. For comparison, Jurassic Park took a little over two years to make with 25 months of preproduction and around three months of principal photography. That's pretty impressive when you consider ILM didn't have the tools Hollywood has today and had to create computer-generated effects that were thought to be impossible at the time.

Daito is a callback to Akira Kurosawa

Daito (Win Morisaki), a member of the "High Five," plays a much larger role in the novel and has a much more tragic ending than he does in the film. Nevertheless, Spielberg wanted his character to be a walking homage to the filmography of revered Japanese filmmaker Akira Kurosawa. Daito's avatar in the OASIS resembles an updated samurai from Japan's Edo Period, but it doesn't end there. Under his helmet, he has a facial mask based on the visage of actor Toshiro Mifune, a longtime collaborator of Kurosawa, who starred in movies like Rashomon, Seven Samurai, and The Hidden Fortress.

Tye Sheridan took Ernest Cline's DeLorean for a joyride

Parzival's preferred mode of transportation is Doc Brown's time-traveling DeLorean from Back to the Future, directed by Robert Zemeckis and produced by Spielberg. According to the book, Spielberg got rid of many references to his own movies in the script, but insisted they keep the DeLorean. Fans of the trilogy now collect the discontinued vehicle and some have even built them from scratch by purchasing DeLorean pieces on the internet. Ready Player One author Ernest Cline owns one and invited Tye Sheridan (who plays lead Wade Watts) to his home in Austin, Texas, so the actor could take it for a test drive.

"If I hadn't been in the DeLorean before, I wouldn't have known that you can't see out of the rearview mirror because there's a blindspot," Sheridan says in the book. "And it's got this interesting steering wheel that's not a wheel at all. It's just one bar with two handle grips. It was nice for me to get an understanding of what it feels like to actually be in the DeLorean." That experience was key: On the motion-capture set, Sheridan sat in a stripped down version of the car that only had the frame of the door, seats, and steering wheel, so he would have physical things to interact with.

Credit: Insight Editions

Nolan Sorrento’s VR chair was partly inspired by 2001: A Space Odyssey

The movie's main antagonist, played by Ben Mendelsohn, is the cunning CEO of a tech company who wants to control the OASIS and monetize it. Sorrento's got the most advanced VR rig in the game, a spherical haptic chair that doesn't require him to move at all. When designing the chair, production designer Adam Stockhausen took inspiration from the Extravehicular Activity Pods from Stanley Kubrick's 2001: A Space Odyssey.

The Shining shout-out was an homage to Spielberg's friendship with Kubrick

The Shining is not featured in the book, but its major inclusion in the movie is a nod to Spielberg's famous friendship with Kubrick. He even took the directing reins of A.I. Artificial Intelligence when Kubrick passed away in 1999. Stockhausen said that the production considered building exact replicas of the Overlook Hotel, but, in the end, decided to digitally scan the entire 1980 movie, thus allowing them to create the most accurate replicas of the grand hall, winding corridors, and blood-filled elevators. The Shining sequence contains actual (albeit augmented) footage from the original film and retains that grainy quality, as do the avatars of the High Five, giving one "the feeling that you're in a dimensional re-creation of the movie," notes senior visual effects supervisor Roger Guyett in the book. The production, however, did find modern-day stand-ins for those creepy twins and the naked lady in the bathtub.

The Orb of Osuvox is modeled after a 20-sided die in Dungeons & Dragons

One of the most powerful magical artifacts in the OASIS, The Orb is used by Sorrento to create an impenetrable force field around the castle in the film's pull-out-all-the-stops finale. It was also modeled after a 20-sided die often used in D&D. If that wasn't nerdy enough for you, it's housed in the box that contained Gizmo in the first Gremlins movie, another Spielberg-produced project.

Aech's Iron Giant isn't the quite the same one from the original movie.

Aech (Lena Waithe) makes a nice living within the OASIS by fixing up vehicles and taking commissions for building certain things like the Iron Giant, for instance. Nevertheless, the final design for Aech's giant wasn't exactly identical to the one featured in Brad Bird's 1999 animated classic. Since the Giant had to be transferred from a two-dimensional setting to a three-dimensional one, it had to be a lot more detailed.

"We needed Iron Giant to have lots of scale and detail... We had to think of the Iron Giant as a physical thing. What would it actually be made out of?" Grady Cofer, a visual effects supervisor at ILM, says in the book. For inspiration, he visited several museums in London during pre- and postproduction to study Victorian machinery and its abundance of "massive gears, spinning flywheels, and pistons."

Check out the gallery below for a sneak peek at The Art of Ready Player One.