Website no longer Chrome-compatible; link to App is dead.
I couldn't find a "contact us" form for CommonSense.org - writing this review is my way of giving you a heads up about this dead tool for the National Library of Virtual Manipulatives. While I know that the "updated" link on this learning resource listing is 2013, the phase-out of Chome/Java compatibility happened shortly thereafter (they stopped offering it in the Chrome store around 2014 or 2015). It would help if materials on the CommonSense database looked fresh; it may help to have staff review any Website that still requires Java. Sadly, in Dec. 2020, sites requiring Adobe Flash will begin to face the same problem. Screening for these major browser incompatibilities - not small ones, but these really really big ones - could eliminate a lot of frustration.
Note - the National Library of Virtual Manipulatives website tries to link to an "App" version that can be downloaded, and doesn't therefore require Java. However, that entire site - MattiMath.com - is no longer working, and I can find few references on the web after 2018.
How I Use It
I would have used it with instruction of fractions.