HOW
SPRITES
ARE
GROUPED
For
playfield priority and collision purposes only, sprites are treated as four groups of
two sprites each.
The
groups of sprites are:
Sprites 0 and 1
Sprites 2 and 3
Sprites 4 and 5
Sprites 6 and 7
UNDERSTANDING
VIDEO PRIORITIES
The
concept of video priorities
is
easy
to
understand if you imagine
that
four fingers of
one of your hands represent the four pairs of sprites and two fingers of your other hand
represent the two playfields.
Just
as you cannot change the sequence of the four fingers
on the one hand, neither can you change the relative priority of the sprites. However,
just
as you can intertwine the two fingers of one hand
in
many different ways relative
to
the four fingers of the other hand, so can you position the playfields
in
front of or
behind the sprites. This is illustrated
in
figure 7-2.
In Front (Higher Priority)
Playfields
f
Behind
Figure
7-2:
Analogy for Video Priority
System Control Hardware
199
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