Hello!
I made a tower-defence game to learn mobile development.
It has a progression system, achievements and 200+ enemies to shoot.
It features 7 different planets with their own automated map-generation algorithms and a RNG-based upgrade system for the towers.
iOS is under review, but will add in the url once available. Link: https://play.google.com/store/apps/details?id=com.gmail.yodstown.Galaxy_Defence_TD