Left: the left hand side is enough to communicate the answer; the left pattern can be seen without the counterexamples on the right.

Right: the right hand side is enough to communicate the answer; the right pattern can be seen without counterexamples on the left.

Flipping a BP will switch its sorting.

The following is taken from the comments on page BP513 (keyword left-narrow):

Call a pattern "narrow" if it is likely to be noticed in a collection of examples, without any counterexamples provided.

A collection of triangles will be recognized as such; "triangles" is a narrow pattern. A collection of non-triangular shapes will just be seen as "shapes"; "not triangles" is not narrow.

Narrow patterns tend to be phrased positively ("is [property]"), while non-narrow patterns opposite narrow patterns tend to be phrased negatively ("is not [property]").

See keywords left-narrow and right-narrow.

Adjacent-numbered pages:
BP825 BP826 BP827 BP828 BP829  *  BP831 BP832 BP833 BP834 BP835

dual, handed, leftright, meta (see left/right), miniproblems, contributepairs, viceversa, presentationinvariant

boxes_bpimage_three_per_side [smaller | same | bigger]

Aaron David Fairbanks

A similar, but different, solution is "center of mass is on the left half vs. center of mass is on the right half."

See BP972 for the version with examples rotated a quarter-turn.

Adjacent-numbered pages:
BP966 BP967 BP968 BP969 BP970  *  BP972 BP973 BP974 BP975 BP976

nice, precise, spectrum, dual, handed, leftright, rotate, boundingbox, blackwhite, traditional, viceversa, absoluteposition, bordercontent

Aaron David Fairbanks

A similar, but different, solution is "center of mass is above the horizontal vs. center of mass is below the horizontal."

See BP971 for the version with examples rotated a quarter-turn.

Adjacent-numbered pages:
BP967 BP968 BP969 BP970 BP971  *  BP973 BP974 BP975 BP976 BP977

precise, spectrum, dual, handed, updown, boundingbox, blackwhite, traditional, viceversa, absoluteposition, bordercontent

Aaron David Fairbanks