Activision always had big plans for Skylanders. Even before the series made its debut in 2011 with Spyro's Adventure, the company had two more games already in the pipeline. The first was Giants, a competent but altogether somewhat bland sequel that used larger toys as its selling point. Quietly in the background, Vicarious Visions had been tapped to iterate on the concept even further.

The goal was to come up with a large enough shift that it could go toe-to-toe with the next generation of toy-based games. Activision rightly predicted that this would be an emerging genre, and needed something fresh to compete with the inevitable imitators. The result was Skylanders Swap Force.

"We just knew, this was kind of a new genre," Vicarious Visions' Rob Gallerani told Shacknews. "We put together a lot of pitch videos that were really just crazy out-there. We know what's been done, we know what the box is that makes up a Skylanders game.

"It started out as 'Shapeshifters,' and the semantics is important. We were hung up on that for a while, because when you think of a shapeshifter you think more of Odo from [Star Trek] Deep Space 9. They just change. And so we had a lot of concepts where characters didn't have armor or weapons. Like, I don't need armor or weapons because I could just make giant claws. And we showed them to a lot of kids, and the kids thought: these don't really look like Skylanders, they look like monsters. That's when we started getting into the mix-and-match."

Skylanders is rigorously tested on kids, and the young audience shapes every expectation from the development team. From visual and sound designers making sure the characters aren't too scary, to the toy prototypes going through several iterations with the factory to make them child-safe and hard to break.

Keeping that simplicity in mind helped define the mix-and-match mechanic too. Once Vicarious Visions had settled on the concept, it began rough toy prototypes. The earliest model was a crude, over-sized clay piece that connected with an audio jack. It worked, but it was clunky and hard for kids to handle. Worse yet, they might mistakenly think they had broken their toy if they didn't understand how to put it back together.

"Our big pillar for almost everything is we wanted something that just worked," visual development director Brent Gibson said. "That came down to the toys as well." So he set about making a proof-of-concept, grabbing several older figures from a collective toy pool and hacking them up at home. The result was a creature with the head of Dark Spyro, the torso of Prism Break, and the legs of Voodood--all connected by magnets.

It looks awful, but it worked. Gibson shot a short video and sent it to some of his colleagues. "I wanted to prove I could film with one hand and assemble a character with my free hand," he said. Not coincidentally, this echos the motions kids might make while holding a controller. The results were a hit at the office, and defined the direction going forward. The studio still had concerns that magnets might interfere with the RFID, but Gibson's Frankenstein could be placed on the portal and was read as Voodood. That was all the proof Vicarious Visions needed.

Of course, the final Swap Force toys feature two swappable parts, not three. It took some time for the studio to settle on the division of labor between parts. The initial concept revolved around letting kids determine the three main attacks by swapping between head, torso, and legs.

"But we saw a lot of kids, how their play patterns work, and they just weren't using things," Gallerani said. "In addition, when you look at the top half of one of the Swap Force characters, or the bottom half, you can sort of tell what it's going to do. But with the heads, it's just a head." He cited Free Ranger as an example, whose head simply looks like a chicken. Nothing too exciting about that. "You also have a lot of low-level things, like it was a choking hazard and things like that."

The Swap Force characters are such a marked change, in fact, that it requires an entirely new RFID reader. Unlike Giants, this sequel won't have a pack for current players that comes without a so-called "Portal of Power," because the old models simply wouldn't work. Gallerani said a lot of their ideas broke some rules, and this one required some investment from Activision. But the idea impressed Activision Publishing CEO Eric Hirshberg enough to make the plunge.

That said, Vicarious Visions isn't denying the possibility of introducing another new portal in the future. "Our current portal can do a lot, but really the attitude right now is that if a new idea is so cool that it warrants a new portal, then we'll do it," Gallerani said. "Mostly the focus is, if we're going to make you get a new portal, we want to make it worth it."

For Skylanders fans, the hardest choice might come down to the platform. In a hands-off demonstration, the PlayStation 4 version looked significantly better than that of the current generation consoles. Though the current-gen versions are still a marked improvement over the previous games, featuring more natural animations and varied environments, subtle changes like extra lighting effects and textures on next-gen systems really make it shine. With the game due in less than a month and the next-gen consoles not coming until mid-November, series devotees may have to choose whether or not to wait it out.

For more on Swap Force, check out our hands-on impressions from E3.

This Skylanders Swap Force preview was based on an event where transportation and accommodations were provided by Activision.