Left-sorted Problems often have a specific format or deal with specific geometric shapes.
Almost any Problem that sorts the all-white or all-black panels will be sorted right.
Adjacent-numbered pages: BP1159 BP1160 BP1161 BP1162 BP1163  *  BP1165 BP1166 BP1167 BP1168 BP1169
notso, meta (see left/right), links, problemkiller
visualbp [smaller | same | bigger]
Leo Crabbe