This morning Subatomic Studios unveiled that it has been doing something other than pounding out updates for Fieldrunners on iPhone and iPad. It’s been working on a big budget sequel to that 2008 original. In fact, Subatomic has been building Fieldrunners 2 since Fieldrunner‘s initial release, carefully toying around with new concepts while also playing around with other prototypes. So, yeah, this one did take awhile.

It’s true that this sequel ushers in the usual, not-so-exciting follow-up fare: new enemies, new towers, new modes, new progression systems, and new maps. But it’s also doing something great and pure. It’s introducing new mechanics that change up the core experience. These tweaks and changes are radical enough that they had Subatomic floating the idea of calling the game something else.

Jamie Gotch, the CEO of Subatomic Studios, chatted with us this afternoon about some of the game’s biggest changes. He also gave us a brief history lesson on how Subatomic got its start, and how important Fieldrunners is to the studio.

“We formed back in 2008. When we first established, we were virtual. We were just some dudes who were working on this game part-time on the side," Gotch says. “We saw an opportunity on the iPhone and we went for it. We had this game idea, which was Fieldrunners, and we figured that — this was before any games were released when the iPhone was in its beta phase and we thought tower defense game would be great to put on a mobile device. There wasn’t much of that out at the time. I don’t know if there were any games that were in that genre. We saw it as a great opportunity. We worked really hard and got the game out and it did really, really well."

Gotch paints an overall picture that has us thinking that Subatomic wouldn’t exist in its current full-time staffed form without Fieldrunners. Subatomic almost … owes that game, and it needs to produce a sequel that feels as honest and hip, but also just as new as Fieldrunners felt at the time.

“We were really fortunate," Gotch tell us when we ask about how many people were buying into the original. “As you know, there’s so many iPhone games out there. It’s very hard to release a game on a huge budget because it’s a huge risk. Fieldrunners has done well and it allowed us the ability to build this team and the game we wanted to build."

One of the things the studio wanted to build for Fieldrunners 2 is better AI. It did, and it’s a game-changer. It’s smarter. It’s now aware of itself and the world it inhabits. Enemies can bump into each other at choke points and push to find safer pathways. They can also scramble over and under each other. The original game was as mechanical as other tower defense games. Enemies just plowed straight ahead, totally oblivious to everything around them — no behaviors, no awareness, no brains.

“In Fieldrunners 2 what we did, we actually have this very elaborate swarming behavior," Gotch says. “Units behave like they would on a real battlefield. If you were to throw hundreds of units on-screen they would all swarm in and take control of the battlefield. Like an army you would see in Braveheart … They actually influence one another. You can build mazes and congest the [pipes you build]. And the guys behind [other enemies] are affected by the guys in the forefront.

Gotch excitedly tells us about other new stuff. Bridges and tunnels are being introduced in addition to environmental hazards and mini-bosses. A really neat sounding collectible card mini-game is in the works, too. As you earn achievements in the game’s modes, you receive cards.

Several of you noted earlier today that the game looks great. It does, and that’s thanks to Fieldrunner 2‘s re-written engine, which is what makes all of the game’s new, much more unpredictable action possible. We’ve got a couple of new screens in the article, so give the game a look as you’re reading.

The new engine and the new AI behaviors combine to make a pretty different game, which is what prompted the debate Subatomic had about the Fieldrunner 2‘s name. In the App Store world, putting a number instead of a subtitle in a sequel’s name is often said to be sales suicide because people quit buying the original game. Subatomic doesn’t care about this. It thinks it created a better game and if it loses sales, whatever. It wants this to stand proudly on its own.

Fieldrunners 2 is due out this June on iPhone and an iPad version will then follow. We talked with Gotch and the game’s lead designer Sergei Gourski on this week’s episode of our bonus podcast. We’ll blast the audio to your earholes tomorrow.