ZXASCII
AUTO -1
PROG demos:graphics/circle_checked
CHANGED FALSE
10 origin 0,0 to 320,192 flip:
 r=68,sx=logw/scrw,sy=logh/scrh:
 for y=4 to 138 step sy:
    y1=71-y,x1=sqr(r*r-y1*y1),y1=y+20:
    for x=78 to 214 step sx:
       if x>146-x1 and x<146+x1 then
          u=x/256-.5,v=(y/176-.5)*.69,
          l=sqr(u*u+v*v+1),
          dx=u/l,dy=v/l,dz=1/l,
          de,dt=0,y1=y+20:
          for i=0 to 50:
             x3=de*dx,y3=de*dy,
             z3=-3+de*dz,
             a3=.97*y3+.26*z3,
             z3=-.26*y3+.97*z3,
             y3=a3,
             a3=.97*x3-.26*z3,
             z3=.26*x3+.97*z3,
             x3=a3,
             dt=sqr(x3*x3+(z3-1)*(z3-1)+y3*y3)-1:
             if dt<.0001 then
                i=50,c=abs int(x3*20)+int(z3*20):
                if (c-2*int(.5*c)) then
                   plot x,y1:
                end if:
             end if:
             de+=dt:
          next i:
30    next x:   
 next y