Pretty typical game.  The CPU runs at 400KHz.  There's one weirdity 
though.  The feeper also drives button reading for the player count
and the A button.

The feeper is simply wired across these two ports so they would
toggle the two ports LH then HL to make it feep most likely.

The 1/2 player select is probably only polled once at the start of
a game, and then the code most likely keeps it at the state where it
reads button A the rest of the time when it's not feeping.