ZXASCII
AUTO -1
PROG demos:colour/curvature blindness
CHANGED FALSE
10 REM Curvature blindness illusion

20 m,o,s=0,wc=7,rh=48,rg=8,ofs=(rh/2-(rg/2))

30 POLYGON INK 15;0,0 TO SCRw/2,0 TO 0,SCRh/2 FILL
40 polygon ink 0;scrw/2,scrh-1 to scrw-1,scrh-1 to scrw-1,scrh/2 fill

50 for y=0 to scrh step rh:
    for x=0 to scrw:
       n=even((x+(m*wc/4*tau)+o)/(wc/2*tau)):
       py=sin(x/wc)*4+ofs:
       plot ink 232+(16*n);x,py+y;x,py+y+rg:
    next x:
    m=1-m:
 next y:

 s+=1,o+=(s mod 100<11),m=0

60 wait screen: cls:
 GO To 30