The main game input is driven by functions starting at A72F. The routine
is entered at different points with HL pointing to a table -
A752, A75C or A764. Each table has the following format:
A byte containing the count of keyboard entries
A pair of bytes for each keyboard entry; the first containing the input to IN A,(FE), the second
containing a bitmask of the expected value if an appropriate key was pressed
A byte containing the appropriate bitmask for a Kempston joystick