for i=1 to ni do {
for j=1 to nj do {
line shaded rgbstring(0,0,1) \
from B.sw+((j-1)*cellw,(i-1)*cellh) \
right c60 up s60 then right 2*s then up s60 right c60 then left s \
then down cellh left 2*c60 then left s
line shaded rgbstring(1,0,0) \
from B.sw+((j-1)*cellw,i*cellh) \
right s then down cellh right 2*c60 then right s then up s60 left c60 \
then left 2*s then left c60 up s60
}
}
PE
