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lovebyte2023: update READMEs

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Vince Weaver 2023-02-12 09:34:16 -05:00
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demos/lovebyte2023/field_16/README Normal file
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This is yet another tiny Apple II hires/shapetable intro.
It loads at $E7 (HGR_SCALE) so that we set that value
for free from the first instruction (in this case JSR so $20).
I thought this result at times looked like a field of grain,
hence the name.
I found this one while doing a search of ROM values that were
easy to load the address for, but the results looked nice.
In this case the rotation and ROM address are $F6 and $F6F6
which makes it easy to load them in a small amount of space.

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demos/lovebyte2023/loveduck_512/README Normal file
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512 byte bootsector demo for the Apple II
I had more elaborate plans for this one, including having the duck
appear randomly over the screen. Ran out of time and also out of bytes.
I also wanted a quacking noise, but couldn't figure out how to do that
in the bytes available.
This is an actual bootsector (well, Apple II has 256 byte disk sectors,
but the disk boot ROM will let you specify more than one to load). Apple
II loads the boot sector starting at $800, which is a problem for a
Lo-res demo as that's also the location of lo-res PAGE2 graphics. So I
had to waste a chunk of code to move the code out of the way before
running it.
The spinning lo-res logo is actually using the hi-res shape table routines.
How is that possible? It draws a small rotating copy of the logo to
the upper-left corner of the (not-displayed) hi-res screen. Then the code
copies this (while adding more colors) to the lo-res screen. It's hard
to do this quickly, to save time and space it actually destroys the hi-res
image by shifting it down to zero while reading it out,
but this is actually good as then we don't have to clear the screen.

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demos/lovebyte2023/weave_16/README Normal file
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This is yet another tiny Apple II hires/shapetable intro.
It loads at $E7 (HGR_SCALE) so that we set that value
for free from the first instruction (in this case JSR so $20).
I thought this looked like woven cloth at times, hence the name.
I found this one while searching for pleasant looking patterns
in the ROM to display that were easy to load. Specifically patterns
that have a 0 value after one or two bytes, as those are smaller shapes.
In this case this is rotation value $E2 at address $E2E2 which is
easy to load.