how do you flip a tile upside-down?

You can rotate a BG tile 180deg with "BGPUT L,X,Y,C OR &H2000", and you can flip a BG tile vertical with "BGPUT,L,X,Y,C OR &H8000". L is BG layer number, and C is BG character number(0-4095).

You can also use the built-in constants #BGROT180 and #BGREVV instead of &H2000 and &H8000, which might make your code more readable.

thanks so much guys you are a huge help :)