Unlike most games for cellular phones in the United States, "Momentum" lets Allen Eichler challenge up to five people from just about anywhere in the country to collect coins scattered throughout a maze.

As millions buy increasingly powerful cell phones, many companies are racing to develop video games to take advantage of the newfound portability.

The newest twist is multiplayer: You can face real people in space battles or fishing tournaments. Until recently, multiplayer on cell phones game meant, at most, posting high scores on a leader board.

Eichler, the creator of "Momentum," said true multiplayer games are a challenge.

There are technical hurdles with pumping game information through slow cell phone networks and with tuning computer servers to handle mobile multiplayer games.

There's also the question of availability. For now, "Momentum" runs on a limited number of handsets offered through Verizon Wireless.

During a recent demonstration, Eichler and several colleagues at Blue Ridge Games Inc. challenged a reporter to a round. In real time, the players maneuvered their characters around a maze to pick up eight coins. The first one to get all eight coins and exit through an escape hatch won.

"We really wanted to find a place where we felt people were ignoring an opportunity," Eichler said. "For a lot of people, one of the most expensive high tech devices that they carry around with them is going to be with their phone."

But don't hold your breath just yet for a miniaturized version of three-dimensional online role playing games such as "EverQuest." The market for cell phone games remains a niche in the overall U.S. video game business, though experts think it will grow to $1 billion in the United States within a few years.

Market research firm Gartner Inc. said sales of handsets are up some 35 percent in the second quarter to 156 million, compared with 116 million a year ago, with sales projected to reach 650 million for the entire year.

Many of the new phones have color screens, extra memory, fast processors and other enhancements.

Like custom ring tones and graphics, the games are downloaded directly to the phone and usually cost a few dollars a month.

Demand for games has risen as owners realize what their phones can do, said Matthew Bellows, vice president of mobile entertainment and co-founder of portable game review site www.Wgamer.com.

"The fundamental truth is that these are network computers, and a common thing that everybody likes to do is play games," Bellows said during the recent Austin Game Conference, a two-day confab of video game designers.

Venture capitalists have invested heavily in the sector in the past few months, and Bellows said most major video game publishers now have either a wireless group or a subcontractor to churn out such games.

Electronic Arts, the world's largest video game publisher, is expanding its lineup of cell phone games for consumers in North and South America and Europe. And EA is also working on new games for Nokia Corp.'s N-Gage hybrid phone/game player and hand-held game devices from Sony Corp. and Nintendo Co.

Nokia's N-Gage is a dual-band cell phone but includes free access to "N-Gage Arena," an online community where people can play each other online, chat and post on message boards, and receive game tips and community news.

In the first-person shooter "Ashen," up to four players nearby can compete against each other using the N-Gage's Bluetooth wireless feature, though long-distance multiplayer gaming is not possible.