SXEKGZVI        Infinite lives
PANYNZLA        Start with 1 life--both players
TANYNZLA        Start with 6 lives--both players
PANYNZLE        Start with 9 lives--both players
VANNVZSA        Player 1 has more lives than player 2
AAOKIZPA        Shoot more bullets
IAVNNZPA + GAVNUZAA     Start at level 5
ZAVNNZPE + PAVNUZAE     Start at level 10
APVNNZPA + YAVNUZAE     Start at level 15
GPVNNZPA + LPVNUZAA     Start at level 20