PlayStation Vita's rear pad a touchy subject

(AP) -- There's a suspicious knock on the wall. A dimwitted henchman working for an evil mastermind named Bakuki goes over to investigate the strange noise and then - WOOSH! - his blotchy body splatters across the room after a giant blade surprises him from behind. That's just one way players can flick their fingers to help heroes Lil and Laarg evade trouble in the cartoony video game "Escape Plan."

That suspicious knock on the wall didn't come from mashing a button or thumping a touchscreen but from tapping the back of the PlayStation Vita, Sony's new high-powered handheld console released Tuesday in the United States and Europe that features a touchpad located behind a touchscreen, giving gamers new ways to engage what's happening on screen.

With the popularity of touchscreen smartphones and tablets, stroking a screen to cut a virtual rope or propel a digital bird is no longer a novel idea, so Sony Corp. is smacking that mechanic on its bottom with a smooth rear touchpad covered with the company's circle, X, square and triangle icons located opposite a lush 5-inch high-definition screen.

Yes, there are old-school buttons and analog sticks as well, but the new interface means Vita users can also interact with images on screen by tapping the rear touchpad, front touchscreen - or both for a "pinching" effect that elicits a different response, like prompting Lil in "Escape Plan" to fart as he floats around Bakuki's twisted headquarters.

"It just feels right to pinch the Vita like that to squeeze the air out of something," said Chris Miller, CEO at "Escape Plan" developer Fun Bits Interactive. "It was a prototype we thought could be a cool game mechanic. We initially tried mirroring what tablets and smartphones do with zoom and camera control, but that actually felt really awkward."

The idea of a rear touchpad isn't entirely new. Motorola has released a few smartphones with a touch-sensitive panel located behind the display screen, replacing the need for a trackball up front, and some itty-bitty handheld keyboards have sported touchpads underneath buttons, but Sony is using the technology for purposes beyond simple navigation.

Several launch titles employ the rear touchpad in different ways: It's a method for climbing ladders in "Uncharted: Golden Abyss," reshaping balls of junk in "Touch My Katamari," accelerating antigravity vehicles in "Wipeout 2048," setting up golf swings in "Hot Shots Golf: World Invitational" and slitting throats in "Metal Gear Solid HD Collection."

For the cart-racing game "ModNation Racers: Road Trip," which invites players to customize their own rides and tracks with the swipe of a finger, developers fashioned the rear touchpad as a way to shape terrain. Push the back of the Vita, a flat surface becomes a hill. Keep mashing, and it becomes a mountain. Too big? Tap the front screen to flatten it out.

"We were able to figure out a way to manipulate the terrain like it was clay," said Sony San Diego producer Brandon Akiaten. "We started out with a single finger, but when we were looking at the entire terrain, we wondered why you couldn't use more fingers, and we were able to create a way to do it, if you can fit all ten of your fingers on the back."

Despite the supercharged quad-core processor inside the Vita, Akiaten said all that instantaneous maneuvering takes precious processing power, which can come at a cost to Vita's battery life and high-definition graphics. The touchy doodad can also sometimes be too sensitive, according to some gamers who've gotten their hands on the front - and back - of it.

"It's a little weird," said college student and hardcore Sony fan Eddie Gonzalez, who stopped to test out the Vita at a pop-up lounge that Sony set up steps away from the beach in Santa Monica, Calif. "Depending on how you hold it in your hands, it might think you're pressing on the back touchpad. It's kinda like you always have to be cognizant of that."

William "Bo" Brinkman, a computer science professor at Miami University in Ohio, believes that rear-touch technology could have more practical uses than simply raising virtual mountains and deceiving digital henchman, especially on smaller gadgets like smartphones, where stubby fingers often get in the way of what's being displayed on the touchscreen.

"Whenever there's been a new technology, the most difficult part is always figuring out what it would best be used for," said Brinkman. "I like some of these preliminary ideas, but I'm more interested to see what people come up with. It's so different from anything else we have right now, it's impossible to predict what it could be used for in the future."