move apple drawing out of the nmi interrupt
this indirection is no longer necessary
move all game logic out of the nmi interrupt

drawing is now done in the main game code, by writing into the $07 page,
and the nmi interrupt now just steps through that page and does the
drawing actions described there
simplify a bit more
oops, this isn't necessary anymore
frame skip should be reset on every new game
draw the score
start the ppu dma at the beginning of nmi, not the end

just to ensure that it has enough time (probably not an issue, but why
not)