Robot Rodeo
I found a fun little puzzle on some obscure website that reminded me of Sokoban. However it used animation that I found tedious and interfered with the actual puzzle solving because it delayed the time I could make a move. So I decided go make my own version. Coincidentally I had just learned about the MIT AppInventor that is a toolbox for creating Android apps using Scratch-like drag-n-drop graphical interface. I found using AppInventor to be very fun and fairly straightforward. I was pleased with the finished product, my first app for Android.
The app was available on Google's Play Store for about five years and then Google decided to remove it because it hadn't been updated. They penalized me for writing good software. So I converted it to a web application so anyone can play it in a browser. Play Robot Rodeo.