100 SET WINDOW 0,1279,0,1023
110 REM (0,0) is the bottom left of the display
120 SET AREA COLOR 1 ! Select color one for drawing
130 FOR row=1 TO 4
140    LET n=IP(2^(row+2))
150    LET w=IP(1280/n)
160    LET py=IP(256*(4-row))
170    FOR b=0 TO n-1
180       LET g=b/(n-1)
190       IF n=16 OR n=64 THEN LET g=1-g
200       SET COLOR MIX(1) g,g,g    !  Reprogram color 1 to the gray we want
210       PLOT AREA: w*b,py; w*b+w,py; w*b+w,py+256; w*b,py+256
220    NEXT b
230 NEXT row
240 END