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In a 2011 Iwata Asks interview, Shigeru Miyamoto expressed discontent at the Virtual Boy being marketed as a video game console. He believed it was simply a novelty toy and that it succeeded in that field despite its commercial failure as a game console:

"It was the kind of toy to get you excited and make you think, 'This is what we can do now!' […] as just a fun toy, it's a big success if you break just 50,000 […] [Its] sales generated some buzz, and crossed 100,000, then 200,000, then 500,000-quite a good pattern […] [But] when you think of it as a gaming platform, it becomes a failure."
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In an interview with Metro, Jeremy 'Jez' San of Argonaut Software fame revealed he helped design a virtual reality gaming system named the "Super Visor" for Nintendo, but the system was ultimately cancelled in favour of the Virtual Boy.
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Early iterations of the Virtual Boy also included a gun that could be set on a flat surface, which would project a 3D hologram-like image into the air.
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Attachment The original prototype for the Virtual Boy was blue and was actually supposed to be worn on the player's head like goggles. It had a screen/pad on the controller, the purpose of which is unknown.
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Even though there was an expansion port for two-player modes, the cable that made this possible was never released due to the fact that the system was discontinued so quickly.
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Attachment The Virtual Boy came to be through an exclusive agreement between Nintendo and the Massachusetts-based company Reflection Technology, Inc., who had developed a monochrome red LED eyepiece display called Scanned Linear Array. General manager Gunpei Yokoi kept the red LEDs while developing the console instead of using a full-color LCD display for several reasons. Both companies claimed color LCDs would have been prohibitively more expensive, retailing at $500 ($1000 when adjusted for inflation in 2023), and tests of the displays were said to have caused visual glitches such as "jumpy images" and players "[seeing] double" instead of seeing depth. Yokoi preferred red LEDs as they were the cheapest option and used a more recognizable color, and unlike a backlit color LCD, he believed the contrasting black color could add a more immersive sense of depth.

It should be noted that a full-color LED Virtual Boy was impossible to release in 1995 due to the fact that high-efficiency blue and green LEDs only became available in 1996. The Virtual Boy, which uses an oscillating mirror to transform a 1-D line of dots to a 2-D field of dots, requires high-performance LEDs in order to function correctly. Without the high-efficiency blue and green LEDs, the Virtual Boy was limited to the red LED display.
person ThisGuyInTheSuit calendar_month March 23, 2013
GamePro Issue #67 (February 1995) (Page 162 in the magazine):
https://retrocdn.net/images/c/c7/GamePro_US_067.pdf

Steven Boyter - A Virtual Failure: Evaluating the Success of Nintendo's Virtual Boy (article from "The Velvet Light Trap" volume 64, issue #64, pages 23-33 in the journal):
https://archive.org/details/VirtualFailure/mode/2up

Steven L. Kent - "The Ultimate History of Video Games: The Story Behind the Craze that Touched our Lives and Changed the World" (Page 514 in the book):
https://books.google.com/books?id=PTrcTeAqeaEC

Fast Company article:
https://www.fastcompany.com/3050016/unraveling-the-enigma-of-nintendos-virtual-boy-20-years-later

Kevin Rafferty - Super Mario takes leap into three dimensional space ("The Guardian" newspaper article, November 16, 1994):
https://www.proquest.com/docview/294877556/4C825E3013B347F4PQ?sourcetype=Newspapers

Planet Virtual Boy Hardware Database:
http://www.planetvb.com/modules/hardware/?type=vb