Sometime last year in November, 2018, I participated in a 1 hour game development challenge using the Unity3D engine and C# for the logic.
The game had to be small, but fun - so a puzzle game was the first to come to mind. I personally enjoy the games that confuse you, so this is the type of game I decided to develop.
The result was posted to Google and was successfully placed on the play store. It is free and can be downloaded from here.