Which of these mathematical education products was widely considered a retail failure despite significant initial hype and investment?

The mathematics industry has seen various products aimed at making calculation and mathematical visualization easier. However, not all innovations have succeeded in the marketplace. This poll tests your knowledge about a notable retail failure in the mathematics education sector - a product that promised to revolutionize how we teach and learn math but ultimately failed to add up to commercial success.

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CAS-puter: The 1997 specialized computer with built-in Computer Algebra System that was priced at $2,500 and became obsolete within months due to software integration in standard laptops
Math-O-Vision: The 1995 augmented reality device that projected 3D geometric shapes but suffered from technical limitations and high production costs
NumLock: The 2002 handheld device that promised to teach advanced calculus through gamification but was criticized for oversimplifying complex concepts
Formula Pen: The 2008 digital pen that could recognize handwritten equations and solve them, but failed due to poor handwriting recognition and battery issues