Runic Games' debut title, 2009's PC action RPG, has sold "well over" 600,000 units since its debut nine months ago, studio CEO Max Schaefer told Gamasutra in a recent interview.What surprised Schaefer about the game's sales was the heavy slant towards digital downloads, as opposed to boxed sales. The game released in October 2009 as a download, and January 2010 at retail."I would say it's almost four-to-one," he said when asked to estimate the ratio of digital downloads to boxed sales. "I think that will even up as time goes on, just because there are different markets -- I think boxes last a little longer in terms of their sales curves -- but right now it's four-to-one, and that's conservative."In May this year, the studio publicly reported that the $20 game sold 500,000 units 's sales may seem modest compared to a high-profile console release, but the game was developed at a substantially lower cost than typical high-budget console games, which can sometimes hit 1 million in sales and be considered a commercial disappointment."We expected that things had moved to digital downloads from boxes since the last time we published and put [out a game]," Schaefer added. "But we were kind of struck by just how far that's gone now.... That's something we have to realize, that that's where the market is for this type of game, and we should really be playing towards that."The 29-person Seattle, WA-based studio is currently working on the newly announced Torchlight II , alongside aMMO.Schafer said the originalhas had decent legs, with sales trailing off by about 10 percent "every week or so." But he added, "It still sells like crazy every time it goes on sale."