prog8/examples/cx16/circles.p8

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%import graphics
; note: this program is tuned for the CX16, but with some minor modifications can run on other systems too.
main {
const ubyte MAX_NUM_CIRCLES = 80
const ubyte GROWTH_RATE = 2
uword[MAX_NUM_CIRCLES] circle_x
uword[MAX_NUM_CIRCLES] circle_y
ubyte[MAX_NUM_CIRCLES] circle_radius
ubyte num_circles = 0
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ubyte background_color
sub start() {
graphics.enable_bitmap_mode()
repeat {
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background_color = rnd()
graphics.clear_screen(0, background_color)
num_circles = 0
draw_circles()
}
}
sub draw_circles() {
uword @zp x
uword @zp y
ubyte @zp radius
while num_circles<MAX_NUM_CIRCLES {
x = rndw() % graphics.WIDTH
y = rndw() % graphics.HEIGHT
radius = GROWTH_RATE * 2 ; use a bit of a buffer between circles.
if not_colliding() {
radius -= GROWTH_RATE
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ubyte color = rnd()
while color==background_color
color = rnd()
graphics.colors(color, 0)
while not_edge() and not_colliding() {
graphics.disc(x, y as ubyte, radius)
sys.waitvsync()
radius += GROWTH_RATE
}
circle_x[num_circles] = x
circle_y[num_circles] = y
circle_radius[num_circles] = radius - GROWTH_RATE
num_circles++
}
}
sub not_colliding() -> bool {
if num_circles==0
return true
ubyte @zp c
for c in 0 to num_circles-1 {
if distance(c) < (radius as uword) + circle_radius[c]
return false
}
return true
}
sub distance(ubyte cix) -> uword {
word dx = x as word - circle_x[cix]
word dy = y as word - circle_y[cix]
uword sqx = dx*dx as uword
uword sqy = dy*dy as uword
return sqrt16(sqx + sqy)
}
; sub distance(ubyte cix) -> uword {
; float dx = x as float - circle_x[cix]
; float dy = y as float - circle_y[cix]
; return floats.sqrt(dx*dx + dy*dy) as uword
; }
sub not_edge() -> bool {
if x as word - radius < 0
return false
if x + radius >= graphics.WIDTH
return false
if y as word - radius < 0
return false
if y + radius >= graphics.HEIGHT
return false
return true
}
}
}