prog8/examples/cx16/kefrenbars.p8

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%import palette
%import math
%import gfx2
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%option no_sysinit
; Vertical rasterbars a.k.a. "Kefren bars"
; also see: rasterbars.p8
main {
sub start() {
uword[32] colors = [
$000,
$011, $112, $213, $214,
$315, $316, $417, $418,
$519, $51a, $62b, $62c,
$73d, $73e, $84f, $94f,
$93e, $83d, $82c, $72b,
$71a, $619, $618, $517,
$516, $415, $414, $313,
$312, $211, $100
]
palette.set_rgb(&colors, len(colors))
gfx2.screen_mode(4) ; lores 256 colors
cx16.VERA_DC_VSCALE = 0 ; display trick spoiler.......: stretch 1 line of display all the way to the bottom
sys.set_rasterirq(&irq.irqhandler, 0)
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repeat {
; don't exit
}
}
}
irq {
const ubyte BAR_Y_OFFSET = 5
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uword next_irq_line = 0
ubyte anim1 = 0
ubyte av1 = 0
ubyte anim2 = 0
ubyte av2 = 0
ubyte[32] pixels = 0 to 31
sub irqhandler() {
next_irq_line += BAR_Y_OFFSET
anim1 += 7
anim2 += 4
if next_irq_line > 480-BAR_Y_OFFSET {
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av1++
av2 += 2
anim1 = av1
anim2 = av2
next_irq_line = 0
; erase the bars
gfx2.horizontal_line(0, 0, 320, 3)
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} else {
; add new bar on top
gfx2.position(math.sin8u(anim1)/2 + math.cos8u(anim2)/2 + $0010, 0)
gfx2.next_pixels(pixels, len(pixels))
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}
sys.set_rasterline(next_irq_line)
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}
}