LOS ANGELES — Nintendo doesn’t mess around with its classic videogame series. It will never release an action game starring its mustachioed mascot Mario until it’s a killer app, a true showcase for the hardware’s features.

[eventbug]So when Shigeru Miyamoto‘s hand-picked team of Mario designers say they’re at work on a Wii U game, we can expect that their creation will be an impressive showcase for the company’s upcoming console. It’s just hard to see how at this point.

Wii U’s defining characteristic is a 6-inch touchscreen built into the game’s controller. It can serve as a control method, a second display or both. You could play games that require a player to look at both screens, or a game might be programmed to display on just the controller screen so that someone else could use the television.

Which will the next Mario game use? Nobody knows yet, especially since the producer of the games says even he wasn’t privy to many of Wii U’s secrets prior to E3.

“As a developer at Nintendo, I had some information about the new system, but I didn’t really have all of the information prior to the announcement at our presentation,” said Super Mario producer Yoshiaki Koizumi in an interview last month at E3 Expo, the annual videogame conference here.

“I only knew some of the things that were considered to be safe,” he said.

Nintendo’s Storied Secrecy

Nintendo is legendary for its secrecy. While many announcements from its rivals often leak ahead of their E3 presentations, it’s rare to see Nintendo’s big projects before the company is ready to unveil them. This is all thanks to Nintendo’s tight security — even its own core employees operate on a need-to-know basis.

With the cat officially out of the bag, Wired.com spoke to Koizumi and The Legend of Zelda producer Eiji Aonuma at E3 Expo to pick their brains about how their games might use Wii U’s unique controls.

Nintendo showed a game called New Super Mario Bros. Mii at E3, but this 2-D series of games isn’t Koizumi’s department — he’s the head of the team that makes 3-D games like Super Mario Galaxy . Koizumi says his team will make a game in the series for Wii U, but that it’s still in the early phase.

“We’re always asking ourselves questions like this as we’re researching new games, about the opportunities presented by the hardware,” he said.

Although the Super Mario Mii demo was used to show how the Wii U can display a single-player game on the television or controller, Koizumi’s thoughts went elsewhere when I asked how he might want to use the Wii U controller.

“When I think about the two screens being used at the same time, it seems like an interesting opportunity to allow us to create a console game where two people are playing at the same time but can’t see each others’ screens,” he said. “It’s certainly an interesting approach, but I have to clarify that it’s not something that we’re working on just yet.”

Koizumi said he worked on something similar years ago, a game that connected the Nintendo 64 and original black-and-white Game Boy systems to play on two screens. But he clammed up when I pressed him for details, only saying that it was a feature that was cut from The Legend of Zelda: Majora’s Mask .

“The information’s going to be shared at some point, but I don’t think today’s the time,” he said.

The Legendary Fake-Out

One of the features of Wii U that Nintendo’s hard-core fans are most excited about is that the company is finally catching up to its competitors and adding high-definition graphics to the new console, which it plans to release in the latter half of 2012. The prospect of exploring Zelda dungeons in 1080p is enticing, which is precisely why Nintendo chose to illustrate the system’s HD graphics at E3 with a real-time Zelda demo.

The brief scene showed Link, the hero of the series, battling a gigantic, hairy, realistic spider. The dark visuals were a sharp contrast to the bright pastels of Skyward Sword , the upcoming Wii game. Eiji Aonuma, producer of the series, says we shouldn’t read too much into the switched-up graphic style.

“You probably remember that when we introduced the GameCube, we showed a somewhat realistic Zelda demo,” he said. “And what we actually created was the cel-shaded Wind Waker . So when we show a graphic demo, people think, ‘Oh, this is what the next Zelda will look like,’ but that’s not necessarily the case,” he said.

‘People think, “Oh, this is what the next Zelda will look like,” but that’s not necessarily the case.’

Indeed, Aonuma said, his team was already hard at work on the cel-shaded, bright, cartoony The Legend of Zelda: The Wind Waker when Nintendo showed that fake-out GameCube demo.

As of now, Aonuma’s team is currently in year five of development on The Legend of Zelda: Skyward Sword , which will be one of the final games for the current Wii console when it ships later this year.

The Zelda team, all hard at work on Skyward Sword , didn’t make the Wii U tech demo, Aonuma says, although he noted that Satoru Takizawa, art director of Legend of Zelda: Twilight Princess , headed up its production.

In contrast to Koizumi, Aonuma said he was more deeply involved in the creation of Wii U.

“I’m on one of the committees that oversaw the general steering and direction” of the new console, he said. “We talked to each other a lot about several elements, one of which was, ‘How exactly will the HD graphics work?’ In doing concepts for that … we used Zelda assets quite often to examine, OK, how real will we make this look?”

Besides illustrating how the high-definition graphics on Wii U might look, the Zelda tech demo showed how Wii U’s controller might aid players of the complex action-adventure games, which revolve around using a massive inventory of weapons and items. In the demo, the player could display his inventory and dungeon map on the lower screen, or flip it to the television screen for easier viewing.

Surely this will be a feature in whatever real Wii U Zelda game that Aonuma creates, right?

“I’d like to do things that are more surprising than that,” he said with a laugh.