Complex sentence: Word Munchers is a spin-off of "Number Munchers" designed to teach basic grammar skills, it was popular among American schoolchildren in the 1980s and 1990s and was used as a teaching aid widely used in schools.
Split into simpler sentences: Word Munchers is an educational game designed to teach basic grammar skills, it was popular among American schoolchildren in the 1980s and 1990s. Related to the game Number Munchers, it was a teaching aid widely used in schools.