Soft, life-sized interlocking building blocks have become a hit at the Parks and Recreation Center, fostering creativity and social development, parents say.Elgin’s rec center received a set of Imagination Playground’s big blue blocks via grant earlier this month, which have since found favor among both children and parents as a cool biweekly summer getaway. Hosted for children ages three through 12, Tuesdays and Thursdays at 3:30 p.m., parents can come create feats of engineering with their young ones or get a workout in while a volunteer room monitor watches over them.“I told them this morning it was blue blocks day ...