Re: Wall Defence game for Apple II

[mmphosis <markwstock@yahoo.com>]

On Apr 24, 11:49 am, winston19842005 <bjjlya...@NOSPAMbellsouth.net>
wrote:
> On 4/24/10 2:09 PM, in article
> _vCdnZJ7Qblbrk7WnZ2dnUVZ_gSdn...@giganews.com, "Michael J. Mahon"
>
> <mjma...@aol.com> wrote:
> > eriknoc wrote:
> >> I like the idea of porting games to the Apple II series.  Nice work,
> >> except it's very difficult to aim & control because he keeps moving,
> >> and fast, and having to press another direction or key to make him
> >> stop takes some of the fun away from playing the game IMHO.  Is this
> >> how it works on ports to all the other systems?  I would have made it
> >> to where letting go of a key or direction would make you stop and
> >> holding it down would make you go.  That would make more sense to me
> >> anyways.
>
> > That kind of control can be implemented on the Apple //e and later
> > machines, but the ][ and ][+, like many other computers of the day,
> > cannot sense when a key is released.
>
> I'm trying to get my head around this statement...
> Why not? What does the keyboard return after you stop pressing a key?
> Does it not return a special value for "no key"?
>
> Signed,
>
> Confused?

I think that Michael J. Mahon is referring to this:

STROBE =   $C010 ;clear bit 7 of keyboard data ($C000)
If read, it also provides an "any key down" flag in bit 7, with
the keycode in the remaining bits. (These features only apply to
the IIe and later machines.)

http://home.swbell.net/rubywand/csa2pfaq.html#004

Althought, this note doesn't mention "key up" only "any key down."
Can you really detect "key up" on Apple IIe and later models?  And if
you can, how is this done?  Documentation?