Ignore my previous post. I'm on crack.
I mean a page *is* 256 bytes, but....I was thinking you only need one set of zeros,
not two. And you do need two sets.
If you really want to get nasty, you could break your screen into multiple variable
length kernals.
Pseudocode:
VSYNC
ldy BallPosition ; y holds the line counter
do stuff above the ball
loop on y (dey) until it's zero
turn on the ball
ldy BallHeight
do stuff during the ball
loop on y (dey) until it's zero
turn off the ball
ldy ScreenHeight-BallHeight
do stuff below the ball
loop on y (dey) until it's zero
It's ugly, but you only have to waste 12 cycles or so per screen...there are
2 lines where you have to reload y and toggle the ball on/off. But you more than make
up for that by not writing to the ball on every line. And you don't burn 2 pages
of ROM for a full height screen kernal.
-Chris
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