Yeah, since I started my game development journey I'm analyzing each game and try to think of how they did it :D
Thank you very much for the explaination on the shadow check.
If you love rotationary games, you could check out my "Rotate Game". Don't judge the name :D I did this game a little over 1.5 years ago for Android and put it on itch now. In the Android Store it is not available at the moment. You should try to finish level 15 because then the endless mode unlocks which is the best part about this game :D