Mario and Sonic's LUATastic adventure

Mario and Sonic's LUATastic adventure  is a game for the PC created by Google made to teach people how to type with the help of Mario and Sonic. It was released in 2011 for 5 bucks and was made freeware in 2016. The game encourages users to learn LUA by helping Mario and Sonic go through their own levels and once they feel like they're ready, the user can take on real world LUA challenges to test their skills.

Retention
The game has sold only 60k copies making it an overall failure and a small hit on Google's financial standings. According to the developer "While most people believe that it is a great way to teach kids how to program, the general public are just not interested in seeing Mario and Sonic teach kids math, typing, and now programming" The game has became freeware afterwards.