Valve's belief was not unfounded, as Steam became the most common method of PC game distribution by late 2009: even earlier, internet distribution surpassed its physical counterpart, and as of mid-2011 is unchallenged. Many, if not most games by most publishers for the PC, not only Valve, are released as "Steam" electronic copies which regularly outsell physical copies. In addition, Steam's DRM remains one of the most secure available, but is very non-intrusive compared to schemes like SecuROM, which, in installing kernel-mode drivers (often somewhat inaccurately referred to as "rootkits"), are often incompatible with certain hardware configurations and many pieces of third-party security software (such as software firewalls and anti-virus applications), a problem that does not plague Steam. Steam also allows consumers to back up their copy of "Half-Life 2" as well as other games that are downloadable through Steam onto CDs or DVDs. To complement this feature many fans have created box coverings for jewel cases that can be downloaded and printed, giving birth to a wide variety of game packaging styles and designs. Java games for cellphones are distributed almost exclusively via the internet. It is possible that the proliferation of home broadband will lead to electronic distribution for all games in the future, leaving physical packaging a niche market, though game developers cite the unsolved problem of digital rights management as the main barrier to this. The earliest consoles had game "cartridges"; the Intellivision cartridge packaging featured a box color-coded to the "network" or category of the game (one of several themes, such as "action", "sports", etc.). The front cover opened up, book style; on the inner front cover, a slot retained the paper manual – a simple booklet, as well as the poly controller overlays. In the main confines of the box, a plastic tray was recessed into which the cartridge fit snugly. When other companies began to produce cartridges for Mattel's system, other types of boxes began to appear, such as Imagic's simple cardboard box, which opened from the top to reveal simple cardboard retainers for the cartridge and rules booklet. Unlike PC games, console manufacturers charge a license fee to anyone developing for their machine, and exert a certain amount of influence in the style of packaging. Nintendo, for example, maintained almost completely standardized boxes for SNES games. PlayStation 2, Nintendo GameCube, and Xbox game boxes also conform to the keep case form factor. All cases of PAL region games for PlayStation and Dreamcast are thicker than standard North American and Japanese CD-cases.