Since his arrival at Halas Hall in January, Matt Nagy has made it known to his staff that he has an open-door policy. And through that office door, on the second floor perched above the Bears practice fields, the decor remains limited.

Naturally, there are the obligatory family photos — one from the day Nagy was introduced as Bears coach and another from his honorary visit to Wrigley Field in April.

A University of Delaware helmet sits on the right side of Nagy’s desk. Plus there is a 40th-birthday gift from his four kids displayed prominently on the bulletin board — “40 reasons we love you.”

Oh, and that? Over there on the west wall? That massive whiteboard that measures 10 feet high by 16 feet wide? That may be the most important thing in here.

That’s Nagy’s erasable canvas, an X’s-and-O’s spitball target that has become the Bears’ hub of offensive ideas.

It looks like a playbook pinata exploded with red, blue, green and black lines zigging, zagging, intersecting, curving.

This, Nagy admits, was among his first requests when he became Bears coach. Thus general manager Ryan Pace wasted little time getting a work order processed, understanding the “Beautiful Mind” board represented three of the biggest qualities he quickly admired in Nagy.

His creativity. His collaborative spirit. His attention to detail.

“His mind,” Pace says, “is always going.”

Nagy lifted the “Beautiful Mind” concept from Andy Reid, whom he worked under for the previous 10 seasons with the Chiefs and Eagles. The name was a playful reference to the 2001 film in which Russell Crowe plays a mathematical genius whose world is seen through a prism of equations, formulas and new ideas.

From Reid and mentor Brad Childress, Nagy learned the value of soliciting outside input and blending ideas. He also admired Reid’s never-ending quest to uncover new concepts, new plays, new wrinkles.

That’s a major reason the whiteboard has to be as large as it is.

“It’s so natural for coaches to come in, have an idea and draw it up,” Nagy said. “But then the natural urge is to just erase it. No, no, no. Keep it up there. Now it’s like a note board. Like sticky notes. You put it up. It stays up there. And eventually someone will come back to that and there it is. Boom.”

An idea is triggered. A new discussion begins. The brainstorming process jumps up a level.

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‘Seeing what we’re seeing’

Inside Nagy’s Halas Hall office, on this “Beautiful Mind” board, the Bears’ innovative offense will continue to take on new life. It is here where the 40-year-old coach and his staff will figure out ways to shape their system in a way that makes quarterback Mitch Trubisky most comfortable and confident.

“It all has to start with the quarterback seeing what we’re seeing,” says offensive coordinator Mark Helfrich. “If you can’t teach that concept to the quarterback, it doesn’t matter how good the idea is.”

During his five seasons in Kansas City, Nagy developed a strong connection with veteran quarterback Alex Smith. Their back-and-forth became a major factor in how the Chiefs offense evolved.

Nagy valued Smith’s experience, how he had seen every defense possible and could envision different ways to attack. Nagy looked forward to Smith’s input.

“He can’t just come in and expect to be the offensive coordinator,” Nagy says. “But you have to listen to what he’s saying and try to fit it into what you want to do as a coach.

“When you can get that flowing and mixing together and molding, it’s awesome. Now you take that to the field and it all clicks. He knows a certain play is coming in on third-and-11 before it comes in. Now you’re rolling.”

Adds Bears backup quarterback Chase Daniel, who was with Nagy and Smith in Kansas City from 2013 to 2015: “We’d be going through a list of a hundred plays and Alex would be like: ‘I don’t like this one. I don’t like that one. Don’t call this one. Let’s call this instead.’ And Matt would adjust to what Alex wanted.

“He understands that if the quarterback feels confident, he’ll make it work. He’ll find a way to get that completion.”

Eventually, as Trubisky builds up a library of plays he has run and defenses he has faced, his voice will become more prominent, more influential. But even now, in the earliest stages of his growth under Nagy, he is encouraged to speak up. Trubisky describes the Bears meetings as “a very inclusive setting” and one fueled by the head coach’s creativity.

Nagy, Trubisky says, is always pushing to add new twists to the offense. A motion. A play-action fake. Anything.

“It’ll be on the spot. Like, ‘Let’s try this. Now,’ “ Trubisky says. “It’s really interesting to see. And it challenges us to think that way too. Like let’s be more creative. How can we take this play and make it a little better?”

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The littlest things

Perhaps at this point, it’s best to also note Nagy’s OCD tendencies, traits for which he is both respected and needled. Like that magnetic silver gadget attached to the whiteboard? When quality-control coach Shane Toub is up on a ladder scribbling play names onto the “Beautiful Mind” board, Nagy wants Toub to put a level on that device and use it to make sure his words don’t sag or angle upward.

They have to be written straight across.

“If the font’s not perfect, if the word is not level, it’s an issue,” Helfrich notes.

Same goes for the colors of the markers. Nagy can’t stand to see two routes intersecting if both are drawn in the same color.

“Can’t overlap black on black,” Nagy insists. “Or red on red. Or green on green.”

Just the thought seems to make his skin crawl. “Those little things kill me.”

True to form, Helfrich says.

“Details matter. That’s the takeaway,” the offensive coordinator explains. “In every way. If you’re a receiver and you’re supposed to be 2 yards outside the hash, then be 2 yards outside the hash. Nothing more, nothing less.”

Details matter indeed.

Over the last 3 1/2 months, Trubisky and Nagy have had meticulous conversations about just about everything. Footwork. Body language. Note-taking techniques.

Everything down to where exactly Trubisky stands when he’s taking the play call.

“That’s important to him,” Trubisky says. “So it’s important to me now too. I’m standing in the right spot getting the play call. I’m walking in (the huddle) with this amount of seconds on the play clock. We’re getting to the line as fast as possible. Now I have time to operate. It’s all those details.”

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Coming to life

When the Bears start the regular season, when they’re in full game-planning mode with a specific opponent and specific players to attack, the “Beautiful Mind” board will come alive. Week by week, the Bears will take their playbook and pick and choose what they want to deploy.

To do so, Nagy understands he’ll need his coaches’ feedback. So with every play that gets considered and drawn onto the board, Nagy goes around the table and asks each offensive assistant whether it’s too much. Yes or no.

“If they think it’s good, they’ll say that,” Nagy says. “If it is too much, why is that? Is it because the tight end has 24 motions? Are there too many shifts? Or is it the concept?”

Listening, Nagy believes, has always been one of his strengths.

“That’s easy for me,” he says. “I’m all for it. The greatest coaches in the world don’t have all the answers. A lot of times they’re the best listeners. And whatever their weaknesses are, they take input from others, and that helps strengthen them.”

Overall, Nagy says, the quest is to find the proper volume of concepts and plays to implement. Frequently, he has noticed, losing streaks can be traced to an unintentional overloading.

“As a staff you say, OK, we were doing way too much,” Nagy says. “We weren’t letting the players play. They were thinking too much. Now let’s pull back. … That whole less-is-more thing.”

At the end of every game week, Nagy takes a photo of the giant whiteboard and files it away. That will then become a reference to evaluate what worked and what didn’t as well as a resource when that opponent comes back onto the schedule.

As Nagy looks up, he grins and shrugs at a marked-up wall that Daniel says represents his “mad genius.”

“I’m a visualizer,” Nagy says. “I want to see everything. It just makes sense. Whether it’s formations, motions, shifts, personnel, a new concept, a play you saw somewhere else, once it’s up there you can zone in and see where the thought process takes you.”

Oh, and for the record, this particular “Beautiful Mind” board is only temporary.

Next year, when the Bears’ Halas Hall renovations are complete and their football operations group has its own wing, Nagy will have a new office.

In there, he says, all four of his walls must include floor-to-ceiling whiteboards. There’s always room for more ideas.