series, or by issuing the songs as downloadable content. The release of Guitar Hero: Smash Hits, reworking older songs from the series to full four-instrument band support but otherwise adding no additional material, was called "the definition of 'milking'" by reviewers, with no observable technical limitation as to why the songs could not be added as downloadable content. Ars Technica recognized that licensing issues might have limited when songs from one single game could be played in others of the series (such as the case for The Beatles: Rock Band), but that such cross-compatibility should have been a high priority for rhythm games. Furthermore, some expansions were praised for the additional content beyond the note-matching gameplay; Guitar Hero: Metallica is considered to be one of the series' best works to be developed by Neversoft in part due to the care that the developers took with imaging the band and the available extras for the game. Activision later revealed that both Guitar Hero 5 and Band Hero would support playing songs from both Guitar Hero World Tour (both on-disc and downloadable content) and Guitar Hero Smash Hits, with music licensing being the only limiting factor on which songs could be made forward-compatible. The large number of Guitar Hero and Rock Band titles on the market is considered to be partially responsible for the sharp decline of music game sales in the latter half of 2009, along with the effects of the late-2000s recession. The market for rhythm games was $1.4 billion in 2008, but dropped to $700 million (a 50% decrease) in 2009 even though more titles were available that year. Former Neversoft project director Brian Bright noted that at one point in 2009, they were responsible for the release of three games that year (Guitar Hero 5, Metallica, and Band Hero) and supporting other studios for the development of two additional games, causing the studio to lose focus both in development and marketing efforts. According to Bright, sales of all the Guitar Hero games released in 2009 totaled the number of sales of the 2008 title World Tour, demonstrating the dilution of the marketing. Though Activision had originally planned on tripling the offerings of the Guitar Hero series in 2010, the company readjusted their plans, reducing the number of offerings and focusing more on selling digital downloadable content for the series. Only two titles, Guitar Hero: Warriors of Rock and