something to keep in mind that I have to deal with once in a while. . . There are vertical 2-player games like 1941 that have the players side-by-side. This won’t work if you don’t have two sticks on one end. For those, you have to UNDO the command above for individual games like this: 1941/display_ror no, assuming you want that. My trackball, for example, is on the horizontal side, so I need to undo the rotation for games like Centipede.
Also, this may be of use to you–on my cocktail style cabinet, I have vertical controls on opposite ends, and if I set the cocktail-mode dip switch for many classics vertical/input_dipswitch[cabinet] cocktail, the screen auto-flips to player 2 on the other end! Again, you may have to reverse this for certain games. Not all games even have the dip switch, but for those that do, like pac man, donkey kong, frogger, etc., this can come in handy. This control layout also works great for Tetris, just like I remember.