Free Windows 10 app: https://www.microsoft.com/en-us/store/apps/the-string-club/9nblggh65m0g
Free Android app: https://play.google.com/store/apps/details?id=us.kusog.stringclub&hl=en
Use this video to learn how to play Counting Stars by One Republic on the viola. Watch the numbers slide down the strings and play the note when it gets to the line at the bottom. It's just like guitar hero for viola.
TheStringClub.com uses viola games to help people learn how to play viola online through easy fun online viola lessons. The String Club provides easy free music lessons for beginner, intermediate and advanced viola players.