By JENNA WORTHAM

c.2011 New York Times News Service

BARCELONA, Spain - It is the modern phone maker's dilemma: In the touch-screen era, how do you stand out from the crowd when most phones are near-identical glassy rectangles?

To get some attention, hardware makers are being forced to find new ways to appeal to buyers who are less interested in particulars like processor speeds than in what applications the devices can run, and how easily they can access their e-mail and Facebook on it.

"At the end of the day, there's only so much you can do with a piece of glass," said Chris Jones, an analyst with the research firm Canalys. "Software can make or break a phone."

At the Mobile World Congress here this week, some phone makers are responding by introducing devices with a twist, hoping that they can grab a buyer's eye with a unique feature like 3-D capabilities. Others, like HTC, are buying or investing in gaming and entertainment companies whose services they can pipe into their mobile devices.

When it comes to applications, the iPhone still has the biggest selection. But phone makers seeking a strong rival to Apple's healthy app economy have turned to Android, the mobile operating system created by Google that is the core software for devices from dozens of manufacturers.

Andy Rubin, one of the chief architects and engineers behind Android at Google, said Android provided the "basic tools" to allow phone makers to create new models faster, since they did not have to worry about the phone's software.

"They can just focus on innovating a better design," he said. "They don't have to worry about adding multitasking and managing memory."

But the rush to embrace Android means that a touch screen phone running the software can easily look like just one of many similar phones.

"Android starts as a base," said Steve Walker, an executive vice president at Sony Ericsson. Phone makers, he said, "still have to build something on top." Sony Ericsson's answer is the Xperia Play, an Android smart phone with a slide-out set of controller buttons, reminiscent of Sony's PlayStation Portable gaming device. The phone is intended to allow users to play games that are too complex for touch-screen controls.

Sony Ericsson also showed off three other phones in the Xperia line, incorporating cameras and other technologies from Sony's half of the partnership with Ericsson of Sweden. The company hopes the devices will help it make headway in the United States, where Sony's brand brings to mind digital cameras, TVs and music players - not necessarily phones.

"In the past we've had trouble getting our devices into the U.S. market," Walker said.

During the weeklong conference here, several other major phone makers have introduced devices with one quirk or another. LG of South Korea, for example, introduced a smart phone with a screen capable of showing 3-D content that does not require any special eyewear.

INQ, a smaller phone maker based in Britain, is hoping to appeal to social networking addicts with a line of Android-based devices that prominently feature Facebook. The home screens of the phones display updates from the owner's Facebook news feed, including images and videos, and provide easy access to chat and check-in functions.

HTC, the Taiwanese hardware manufacturer, is also trying to take a crack at the social networking craze. On Tuesday the company showed two phones, the ChaCha and the Salsa, that include a separate button on the front to quickly access Facebook.

At the show, HTC revealed its first tablet, a svelte device called the Flyer, which comes with a stylus and is outfitted with new software offerings. The Flyer has a movie streaming and downloading application called HTC Watch, as well as access to OnLive, an online service that lets people play elaborate games without buying specialized hardware.

Perhaps the biggest indicator of the challenges facing phone makers is the recent announcement that Nokia has formed an alliance with Microsoft to use its Windows Phone 7 software in its line of mobile devices, moving away from its own home-grown software.

"The world is shifting from a battle of devices to a war of ecosystems," said Stephen Elop, the new chief executive of Nokia who is charged with spearheading the company's turnaround, in a press event here. "Nokia brings hardware and incredible industrial design, and Microsoft has the software."

Nokia, which helped shape the modern cell phone market, has sunk millions into adapting its handset business to the rapidly evolving industry. Many in the industry view the alliance as an acknowledgment that for companies like Nokia, it is no longer enough to build the sleekest new devices.

"They also have to build a content portfolio, know how to attract developers and help them make money," said Al Hilwa, an analyst who follows the wireless industry for the research firm IDC. "Not many companies already have that skill set."

The pressures, analysts say, will only increase as smart phones continue their spread.

Last year, according to the research firm Gartner, global sales of smart phones surged 72 percent compared to sales in 2009. Analysts anticipate that as soon as this year, mobile phones and tablets will eclipse desktop and laptop computers as the primary way people access the Internet.

"It's a very disruptive time," Hilwa said. "Both software and hardware companies are going back to the drawing board and rethinking their business plans."

And once they figure out how to make their phones less generic, hardware makers will have to tackle the same problem with tablets.

"We're seeing a lack of innovation around the design of tablets," said Jones of Canalys. "That's a bigger piece of glass, a bigger black slab to try and differentiate for consumers."