1957 shaares
The DigiRule is a 15cm (6") interactive binary ruler.
http://www.bradsprojects.com/the-digirule/
http://www.bradsprojects.com/wp-content/uploads/2015/10/DigiRule-Files-15-December-2015.zip
was https://www.kickstarter.com/projects/1897710270/digirule-the-interactive-binary-ruler/description
