The rules have changed. Gone are the days of video-game makers headquartered in expensive offices with production centered on seven-year life cycles of popular consoles. Now Xboxes and PlayStations get upgraded mid-cycle, and independent, far-flung networks of game developers rule from virtual studios. Like so many other industries, gaming promotion and sales have been disrupted by the broadband era that allowed product to be distributed digitally. And while the new age is less stable, it has opened the door to wide-ranging innovation — that gamers can purchase from their sofas.