ANAHEIM, Calif. — At a fan gathering here last weekend, the Walt Disney Co. beat the drums for its new Infinity video game, which goes on sale Sunday, by staging an elaborate demonstration of its capabilities, allowing attendees to play it for themselves and handing out Mickey Mouse swag.

But it was an accompanying app called Disney Infinity: Action! that summed up what’s at stake for the company. The app, available free now on the Apple iTunes store and soon for Android devices, allows users to place themselves inside the game and make short videos of the action. As an example, Disney showed a video of a digital Capt. Jack Sparrow aiming a cannon at John Pleasants, co-president of Disney Interactive, and lighting the fuse.

Infinity, which cost Disney more than $100 million to develop, according to analysts, is viewed as a make-or-break effort to turn around the company’s money-losing gaming and Web division after years (and years) of trying.

“It’s the most ambitious creative undertaking we’ve ever done,” Pleasants said Sunday at the D23 Expo, a biennial convention for Disneyphiles.

Infinity allows users to mix and match Disney and Pixar characters in rollicking video game adventures. Players collect action figures — Woody, Mickey, Sulley, Mr. Incredible, Rapunzel — and transfer them into the game’s action by plugging them into a sensor base.

How Infinity will fare is anyone’s guess. Independent sales data will not be available until late September.

It is generating substantial buzz among gamers, an audience that has not always been the friendliest toward Disney. The Infinity booth was mobbed at the D23 Expo last weekend, with people waiting for the chance to take the game for a test drive.