Microsoft gave a sneak peek at its "Halo 3" game on Friday, saying the next chapter of the fast-paced shooter trilogy will help it fend off competition from Sony and Nintendo. Microsoft expects the launch of its upcoming "Halo 3" video game to surpass that of "Halo 2," which pulled down $125 million in sales in its first 24 hours, an executive said on Friday.

Gamers at the invitation-only preview gave mixed reviews.

Microsoft staged previews in New York and San Francisco on Friday in advance of the public test, or "beta," of the game, which goes live next Wednesday.

The company plans to launch "Halo 3" in the autumn. The game once again puts players in control of "Master Chief," a futuristic soldier trying to save humanity from an alien coalition known as the Covenant.

To make things more realistic, game maker Bungie Studios made the movements in "Halo 3" more closely follow the laws of real-world physics.

Dead bodies float. Grenades tossed in snow stay in place, while those thrown on harder surfaces skip and roll. Bullets ricochet off walls. And gamers' characters straying too close to grenades will be maimed by their shrapnel effect.

The games have also driven adoption of the Xbox Live online gaming service, which offers some basic features for free but charges users about $50 a year for being able to play against other gamers.