Sorry, no download of examples.
Do you mean something like:
' ported from a SmallBASIC example
screen (1024,960,"Spiral")
KEY_ESC = 27
cx = screenwidth/2
cy = screenheight/2
pi=3.141
setfps (120)
do
cls
key=getkey
size = 1
radius = .06
angle = sangle
cls
While radius < 400
x = cos(angle) * radius
y = sin(angle) * radius
r2 = (x ^ 2 + y ^ 2) ^ .5
size = 4 * r2 ^ .25
For r = size to 1 step - 2
cc = 160 + 95 * radius/400 - r/size*120
ink (cc, cc, cc)
fillcircle (cx + x, cy + y, r)
Next
angle =angle - .4
radius =radius + 1
Wend
sangle = sangle + pi/360
sync
until key=KEY_ESC
Yes, RetroBASIC works on macOS, too.