How do I prevent overlapping?

Hey guys, I'm sorry if I use the wrong category tag but I couldn't find a suitable one for it, I'm currently making an app with a game call Whack-A-Mole, but in the game the moles are always overlapping. Do anyone have any idea on how to fix this issue, I have been working it for a while but couldn't find a solution for it.

Welcome DingNigaFAi.

Try this similar tutorial MoleMash which does something similar; it may not have the issue you describe.