The first time gamers got an Xbox, they fell in love with a blistering, trigger-happy game starring a space Marine. The first time gamers are getting an Xbox 360, they're falling for a blistering, trigger-happy game starring a space ship. And it barely costs $5.

If you've got an Xbox 360, chances are you've already played "Geometry Wars." And if you've played it, you've discovered the iceberg tip of Xbox Live Arcade, the 360's download service that some gamers and game makers say has the potential to change what people look for in a game console and may even increase the odds that the average Xbox gamer may someday make a game for the system.

" 'Geometry Wars' has been our 'Halo,' " said Greg Canessa, the group manager in charge of Live Arcade.

Since the 360 was launched less than two months ago, the trial version of the game has been downloaded more than 200,000 times, according to Canessa. Nearly 45,000 people have purchased the full game and had their high scores posted on Xbox Live's global-leader board.

The game seems to be popular in part because it is simple: One space ship on one board shoots at waves of enemies that explode in dazzling bursts of light. The appeal is the quest for a high score and the fireworks such a drive produces.

"It's like an interactive version of those acid-trip musical visualization devices," said Epic Games designer Cliff Bleszinski.

"GW" addicts should note that the game's 25-year-old designer, Stephen Cakebread, said he was initially thinking of putting mazes in the sequel. He had also dabbled with multiplayer when working on the original. But he decided to keep the design simple and go for visual splash. "There was something pure about having the open arena and having the enemies come at you," he said. The game worked best when he kept it simple.

The most popular of the Live Arcade titles available, "GW" sits in wait for gamers with an Internet-connected 360. Alongside it are more than a dozen other titles that are free to try and cost between $5-$20 to unlock for fully featured play. The lineup currently includes old-school hits such as "Joust" and "Gauntlet," new games such as "GW" and the space-station builder "Outpost Kaloki," and favorites like "Zuma" and "Bejeweled." Earlier this month the service saw the addition of "Wik: Fable of Souls," which received top honors at last year's Independent Games Festival.

Downloadable gaming is not new. Publishers small and large have been developing and distributing small games over the PC for years via services from Yahoo! and Real Networks to great success. Xbox Live Arcade takes that scenario to TVs.

"Up until the launch of the 360 I was playing more of the current generation games," said Alben Pedroso, 32, a producer at Capcom's Sunnyvale, California, studio. Pedroso said his time is now split between store-bought games and ones on Live Arcade. Bleszinski says he's struck a similar balance.

Pedroso has also been keeping busy producing Capcom's first Live Arcade title, a remake of early '90s classic "Street Fighter II - Hyper Fighting." That game will sport the Live Arcade's first spectator mode, allowing users to not just queue up for challenge matches online but watch a match in progress involving a contestant they're about to play.

As potent as the system may be for the return of old favorites, it's also being positioned to attract game ideas that might otherwise have never made it to a home console. Steve Taylor, president and programmer at Wahoo Studios in Utah, said his company had aggressively pitched the space-station-building game "Outpost Kaloki" to publishers as a store-sold console title. "They all said, 'This game is really fun and it's beautiful and we liked your art style and we liked the music,' " he said. Still, the publishers declined, saying the financial risk was too high. So Taylor pitched it as a Live Arcade title. Canessa's team bit.

The idea that one programmer with a great idea can't make an impact on the system might seem far-fetched, except that notion circles right back to "Geometry Wars." The game was created almost single-handedly by Cakebread, a programmer at "Project Gotham Racing 3" developer Bizarre Creations. He had created an earlier version of the game as a way to test technology for "PGR2" and it quickly became a popular office distraction. The game was tucked into "PGR2" as a bonus, one that was acclaimed enough to mandate a sequel for the 360.

Canessa is not just hoping to attract the developers who have had doors shut in their faces, but even game makers who haven't even tried to break in yet. "We're somewhat overwhelmed with submissions right now," he said. Gamers looking to join the pile can submit ideas through arcade@microsoft.com.

The potential may be there for Xbox gamers to realize their ideas into actual Xbox Arcade games, but it still won't be cheap. Developers interviewed for this story estimated that the cost to create a Live Arcade game could run between $10,000 to $100,000.

Nevertheless a support system is building for gamers to pursue that path. Mark Frohnmayer, president of Oregon developer Garage Games and developer of the forthcoming Live Arcade title "Marble Blast Ultra," said his company will soon begin licensing a version of their Torque game-design toolset for prospective Live Arcade developers.

Canessa said Live Arcade will have 35 games by the summer, with new games each week, including the most-requested Texas Hold' Em Poker. Microsoft's own development teams have two games scheduled for release by the summer, and in-house engineers are working to enable features such as Netflix-style game recommendations.

So there will be plenty more gaming to be done on Live Arcade. Or gamers can just keep plugging away at "Geometry Wars." Cakebread said the game stops getting harder at around 5 million points. A check of the Xbox Live leader board shows that only a handful have breached that threshold. Arcade glory is within reach, if just barely.