Once upon an afternoon, I’ve found Unity game engine, it matched to my criterias (easy to use, mobile deploy, the usual things) and I decided to learn it. I started with the basics. I made a Pong. I spent a lot of hours to make it work, I added extra features, like multiplayer game via Bluetooth, AI against computer, but for some reason it wasn’t enough for Google to release it to Play store.
After a while when I tried to organised my code I had to realised I just lost the source code of my Pong game. Died hard drive never helps. I had to face it I can’t modify it anymore. From that moment I decided to store all my source codes in cloud. I have already a lot of stuffs on Bitbucket, it’s great and free, should work for Unity files too.