This was the basic idea behind LeapFrog, but Wood spent years refining the concept and testing it in various ways. He spent four years doing focus groups on mothers, to see if there was interest and to get their feedback. He had a prototype made, in order to make sure the manufacturing was plausible. He also did studies to work out the cost of manufacturing and a viable retail price. He met with a buyer from Toys 'R' Us to determine interest there. In 1994 Wood took his first prototype phonics toy to Robert Calfee, a professor of education at Stanford. Dr. Calfee had spent 25 years researching how children learn to read, and he took the time to consider Wood's toy. Calfee gave Wood some suggestions, but did not expect to hear back from the inventor. But Wood took Calfee's advice to heart, and within a few months brought the professor a new and improved prototype. This became the Phonics Desk, LeapFrog's first product.