Following up to my own post:
>I think what Rabbit Transit does is loading HMM0 with $70. 18 cycles after
>the next STA HMOVE it does STA HMCLR, wich ends at cycle 21 and seems to
>trick the TIA, too.
>
>I have not tested if the resulting starfield is the same as with a second
>STA HMM0 or a different one, yet.
I have tried it out now. The effect is basically the same, except that
Cosmic Ark does a STA HMM0 during cycles 19, 20 and 21, while Rabbit Transit
does a STA HMCLR during cycles 18, 19 and 20. The $70 in HMM0 when HMOVE is
triggered, seems to be essential.
The resulting starfield is the same. It looks like missile0 is shiftet 15
pixels to the left in every line. But every fourth pixel seems to be attatched
to the third. So the starfield would look like:
x
x
xx
x
x
xx
x
x
xx
x
x
xx
and so on. Positioning the initial missile 15 pixels further right would result
in the whole starfield being moved one pixel to the top right.(This is used
by Cosmic Ark.)
I hope this is clear enough.
Ciao, Eckhard Stolberg
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