Minefield

sw1	attract mode sound
        on = on   off = off

sw2     lives
        on = 4   off = 3

sw3,4   difficulty
        on  on  hard
        on  off 3
        off on  2
        off off easy

sw5     on  1 coin 2 credit
        off 1 coin 1 credit

sw6     on  2 coin 1 credit
        off 1 coin 1 credit