Epic Games last month paid $1.57 million for five undeveloped acres at 600 Crossroads Blvd. adjacent to the 31,000-square-foot headquarters the company built in 2004, county records show.

Epic is in the early stages of planning an office building that would at least double the space on its campus near Jones Franklin Road at Interstate 40. "We've pretty much run out of space here," said Mark Rein, an Epic vice president.

The company has expanded steadily in the past two years as sales of its games and game-development software have grown. It has 94 employees, having grown by about an employee a month, Rein says. That pace is expected to continue for at least two years as Epic churns out more games.

For most companies, that kind of employee growth wouldn't precipitate the need for an entire building.

In this case, the building would be crucial for testers employed, not by Epic, but by the companies that publish its games. Dozens of testers visit each year, setting up at temporary workstations and trying to work out the kinks in Epic's latest games.

Now that Epic is riding the wave of two popular games -- "Gears of War," published by Microsoft, and the "Unreal Tournament" series, published by Midway -- the need for more testing space is pressing. "It tests your resources," Rein said.

"Gears," which was released in 2006, has sold at least 4 million copies, becoming Epic's single most successful title. That's about four times the average number of copies each Unreal Tournament edition sells.

Last year, Epic moved testers to rented offices in Crossroads Corporate Park. But having them next door, instead of down the street, would help things run more smoothly.

"The feedback loop is better," Rein says. "We can sit in a room and say, 'Hey, here's a bug I saw. Can you recreate this and tell me what you think is causing it?' They're constantly playing through the game and testing every little level, and it takes a lot of people to test a game properly."

The booming video-game industry's appetite for Triangle offices is growing as other industries are delaying or canceling expansion plans.

In November, Vicious Cycle Software, which developed games such as "Puzzle Quest" and "Flushed Away," agreed to move from Durham to Morrisville in a deal that would expand its headquarters by about 50 percent to 20,000 square feet.