prog8/examples/cx16/snow.p8

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%import math
%import gfx2
main {
sub start() {
gfx2.screen_mode(4)
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uword[128] flakes1_xx
uword[128] flakes1_yy
uword[128] flakes2_xx
uword[128] flakes2_yy
ubyte @zp idx
for idx in 0 to 127 {
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flakes1_xx[idx] = math.rndw() % 320
flakes1_yy[idx] = math.rndw() % 240
flakes2_xx[idx] = math.rndw() % 320
flakes2_yy[idx] = math.rndw() % 240
}
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draw_screen()
const ubyte FALLING_SNOW_COLOR = 1
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const ubyte FALLING_SNOW_COLOR2 = 12
const ubyte PILED_SNOW_COLOR = 15
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ubyte[] PILED_SNOW_COLORS = [PILED_SNOW_COLOR, 5, 2] ; falling snow colors should NOT be in here!
bool fall_layer_2 = false
repeat {
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for idx in 0 to len(flakes1_xx)-1 {
gfx2.plot(flakes1_xx[idx], flakes1_yy[idx], FALLING_SNOW_COLOR)
gfx2.plot(flakes2_xx[idx], flakes2_yy[idx], FALLING_SNOW_COLOR2)
}
sys.waitvsync()
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for idx in 0 to len(flakes1_xx)-1 {
if flakes1_yy[idx]==239 {
; reached the floor
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gfx2.plot(flakes1_xx[idx], flakes1_yy[idx], PILED_SNOW_COLOR)
flakes1_yy[idx] = 0
flakes1_xx[idx] = math.rndw() % 320
} else if gfx2.pget(flakes1_xx[idx], flakes1_yy[idx]+1) in PILED_SNOW_COLORS {
; pile up
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; TODO somehow prevent growing horizontally/diagonally like a crystal
uword @zp snowx = flakes1_xx[idx]
if snowx!=0 and snowx!=319 { ; check to avoid x coordinate under/overflow
uword pilex1
uword pilex2
if math.rnd() & 1 {
pilex1 = snowx-1
pilex2 = snowx+1
} else {
pilex1 = snowx+1
pilex2 = snowx-1
}
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ubyte pixel_side1 = gfx2.pget(pilex1, flakes1_yy[idx]+1)
ubyte pixel_side2 = gfx2.pget(pilex2, flakes1_yy[idx]+1)
if pixel_side1 == 0 or pixel_side1 == FALLING_SNOW_COLOR2 {
gfx2.plot(snowx, flakes1_yy[idx], 0)
gfx2.plot(pilex1, flakes1_yy[idx]+1, PILED_SNOW_COLOR)
} else if pixel_side2 == 0 or pixel_side2 == FALLING_SNOW_COLOR2 {
gfx2.plot(snowx, flakes1_yy[idx], 0)
gfx2.plot(pilex2, flakes1_yy[idx]+1, PILED_SNOW_COLOR)
} else {
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gfx2.plot(snowx, flakes1_yy[idx], PILED_SNOW_COLOR)
}
}
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flakes1_yy[idx] = 0
flakes1_xx[idx] = math.rndw() % 320
} else {
; fall
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gfx2.plot(flakes1_xx[idx], flakes1_yy[idx], 0)
flakes1_yy[idx]++
when math.rnd() & 3 {
1 -> {
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if flakes1_xx[idx]
flakes1_xx[idx]--
}
2 -> {
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if flakes1_xx[idx] < 319
flakes1_xx[idx]++
}
}
}
}
fall_layer_2 = not fall_layer_2
if fall_layer_2 {
for idx in 0 to len(flakes2_xx)-1 {
; the second 'layer' of snowflakes
if flakes2_yy[idx]==239 {
; reached the floor, don't pile up just fall again
flakes2_yy[idx] = 0
flakes2_xx[idx] = math.rndw() % 320
} else if gfx2.pget(flakes2_xx[idx], flakes2_yy[idx]+1) in PILED_SNOW_COLORS {
; reached an obstruction, don't pile up just fall again
flakes2_yy[idx] = 0
flakes2_xx[idx] = math.rndw() % 320
} else {
; fall normally
gfx2.plot(flakes2_xx[idx], flakes2_yy[idx], 0)
flakes2_yy[idx]+=1
when math.rnd() & 3 {
1 -> {
if flakes2_xx[idx]
flakes2_xx[idx]--
}
2 -> {
if flakes2_xx[idx] < 319
flakes2_xx[idx]++
}
}
}
}
}
}
repeat {
}
}
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sub draw_screen() {
gfx2.text(32, 130, 2, sc: "******************" )
gfx2.text(40, 140, 5, sc: "happy holidays !" )
gfx2.text(32, 150, 5, sc: "from commander x16" )
gfx2.text(32, 160, 2, sc: "******************" )
; draw a tree
const uword TREEX = 240
ubyte maxwidth = 20
ubyte branchesy = 100
gfx2.fillrect(TREEX-5, 210, 10, 30, 9)
repeat 5 {
ubyte width
for width in 1 to maxwidth {
gfx2.horizontal_line(TREEX-width/2, branchesy, width, 5)
branchesy++
}
branchesy -= maxwidth/2
maxwidth += 8
}
}
}