This is a full blown tutorial that has been overdue for two years (Because I made this game a couple of years ago but never got the time to write the tutorial for it). This should teach you how to make a side scroller game with dynamic width/height/positions of components to support various device sizes. This is the longest tutorial and also app inventor game I have ever written! All good learning went to this tutorial. Enjoy!
Tutorial Link: https://www.imagnity.com/android/flappy-copter-create-a-game-like-flappy-bird-from-scratch-using-app-inventor/