Which mathematical product design innovation was specifically created to help visually impaired students learn mathematics, but later became widely adopted in mainstream education?

The design of mathematical tools and products has evolved significantly over centuries, impacting how we learn and apply mathematical concepts. From ancient counting devices to modern digital tools, product design in mathematics has shaped educational approaches and problem-solving capabilities. This trivia question focuses on a pivotal product design innovation that transformed mathematical education and practice.

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Cuisenaire rods
Nemeth Braille Code
Digital graphing calculators
Abacus with color-coded beads