A video game is an electronic game that involves interaction with a user interface to generate visual feedback on a video device such as a TV screen or computer monitor. The word video in video game traditionally referred to a raster display device, but as of the 2000s, it implies any type of display device that can produce two- or three-dimensional images. Some theorists categorize video games as an art form, but this designation is controversial. The electronic systems used to play video games are known as platforms; in addition to general-purpose computers like a laptop/desktop being used, there are devices created exclusively for the playing of video games. Platforms range from large mainframe computers to small handheld computing devices. Video games are developed and released for specific platforms; for example, a video game that is available to Steam may not be available to Xbox One. Specialized video games such as arcade games, in which the video game components are housed in a large, typically coin-operated chassis, while common in the 1980s in video arcades, have gradually declined due to the widespread availability of affordable home video game consoles (e.g., PlayStation 4, Xbox One and Nintendo Switch) and video games on desktop/laptops and smartphones. The input device used for games, the game controller, varies across platforms. Common controllers include gamepads, joysticks, mouse devices, keyboards, the touchscreens of mobile devices, or even a person's body, using a Kinect sensor. Players view the game on a display device such as a television or computer monitor or sometimes on virtual reality head-mounted display goggles. There are often game sound effects, music and voice actor lines which come from loudspeakers or headphones. Some games in the 2000s include haptic, vibration-creating effects, force feedback peripherals and virtual reality headsets. In the 2010s, the commercial importance of the video game industry is increasing. The emerging Asian markets and mobile games on smartphones in particular are driving the growth of the industry. As of 2015, video games generated sales of USD 74 billion annually worldwide, and were the third-largest segment in the U.S. entertainment market, behind broadcast and cable TV.