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BP112 X-coordinates of dots are equidistant vs. y-coordinates of dots are equidistant.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP107 BP108 BP109 BP110 BP111  *  BP113 BP114 BP115 BP116 BP117

KEYWORD

hard, nice, antihuman, traditional

CONCEPT coordinate (info | search),
length_line_or_curve (info | search),
midpoint (info | search),
imagined_line_or_curve (info | search),
imagined_entity (info | search),
same_feature (info | search),
same (info | search)

WORLD

three_points [smaller | same | bigger]

AUTHOR

Douglas R. Hofstadter

BP162 Every other side, if extended, passes through one point vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP157 BP158 BP159 BP160 BP161  *  BP163 BP164 BP165 BP166 BP167

KEYWORD

hard, noisy, traditional

CONCEPT lines_coincide (info | search),
every_other (info | search),
imagined_point (info | search),
imagined_line_or_curve (info | search),
imagined_entity (info | search)

AUTHOR

Harry E. Foundalis

BP344 Shape can tile itself vs. shape cannot tile itself.
(edit; present; nest [left/right]; search; history)
COMMENTS

Left examples are sometimes called "rep-tiles."


The tiles all must be the same size. More specifically, all left examples can tile themselves only using scaled down and rotated versions of themselves with all tiles the same size. Right examples cannot tile themselves using scaled down rotated versions of themselves or even reflected versions of themselves with all tiles the same size.


Without the puzzle piece-like shape EX4120 on the right side the current examples also allow the solution "shape can tile with itself so as to create a parallelogram vs. shape cannot tile with itself so as to create a parallelogram."

CROSSREFS

See BP532 for a version with fractals.

Adjacent-numbered pages:
BP339 BP340 BP341 BP342 BP343  *  BP345 BP346 BP347 BP348 BP349

EXAMPLE

Go to https://oebp.org/files/yet.png for an illustration of how some left-sorted shapes tile themselves.

KEYWORD

hard, precise, notso, unstable, math, hardsort, creativeexamples, proofsrequired, perfect, traditional

CONCEPT recursion (info | search),
self-reference (info | search),
tiling (info | search),
imagined_shape (info | search),
imagined_entity (info | search)

WORLD

shape [smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

BP383 When the shape is removed from the dots, the dots give enough information to place the shape back where it was vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP378 BP379 BP380 BP381 BP382  *  BP384 BP385 BP386 BP387 BP388

KEYWORD

hard, nice, traditional

CONCEPT imagined_line_or_curve (info | search),
imagined_entity (info | search),
convey_enough_information (info | search)

AUTHOR

Aaron David Fairbanks

BP394 For each colored square only, there exists a path starting on it that covers each square of the figure exactly once vs. there is no path that starts on a colored square and covers each square of the figure exactly once.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP389 BP390 BP391 BP392 BP393  *  BP395 BP396 BP397 BP398 BP399

KEYWORD

hard, nice, solved, traditional, dithering, left-listable, right-listable

CONCEPT existence (info | search),
path (info | search),
imagined_line_or_curve (info | search),
imagined_entity (info | search)

AUTHOR

Jago Collins

BP559 Cross section of a cube vs. not cross section of a cube
?
(edit; present; nest [left/right]; search; history)
COMMENTS

All examples are solid black shapes.


This problem is absurdly hard. It makes a good extreme example. - Aaron David Fairbanks, Nov 23 2020

CROSSREFS

Adjacent-numbered pages:
BP554 BP555 BP556 BP557 BP558  *  BP560 BP561 BP562 BP563 BP564

KEYWORD

hard, precise, allsorted, notso, stretch, challenge, left-narrow, perfect

CONCEPT cube (info | search),
cross_section (info | search)

WORLD

fill_shape [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP564 Discrete points intersecting boundary of convex hull vs. connected segment intersecting boundary of convex hull
(edit; present; nest [left/right]; search; history)
COMMENTS

If a "string" is wound tightly around the shape, does one of its segments lie directly on the shape?


All examples in this Problem are connected line segments or curves.


We are taking lines here to be infinitely thin, so that if the boundary of the convex hull intersects the endpoint of a line exactly it is understood that they meet at 1 point.

CROSSREFS

Adjacent-numbered pages:
BP559 BP560 BP561 BP562 BP563  *  BP565 BP566 BP567 BP568 BP569

EXAMPLE

Imagine wrapping a string around the pointed star. This string would take the shape of the boundary of the star's convex hull (a regular pentagon), and would only touch the star at the end of each of its 5 individual tips, therefore the star belongs on the left.

KEYWORD

hard, nice, allsorted, solved, perfect

AUTHOR

Leo Crabbe

BP793 Image of a Bongard Problem that would sort itself on its own left versus image of a Bongard Problem that would sort itself on its own right.
?
?
(edit; present; nest [left/right]; search; history)
COMMENTS

Rhetorical question: Where does this Bongard Problem sort an image of itself?

See BP999 and BP1004 for similar paradoxes.


Bongard Problems fitting left here evidently come in three categories: 1) would sort all Bongard Problems with the same solution left, 2) would sort all Bongard Problems with the same solution right, or 3) would sort some Bongard Problems with the same solution left and some right. See BP927.

CROSSREFS

See BP517 for the version with links to pages on the OEBP instead of images of Bongard Problems (miniproblems).


See BP954, which is about Bongard Problems not only sorting themselves, but moreover fractally appearing in themselves as panels.

Adjacent-numbered pages:
BP788 BP789 BP790 BP791 BP792  *  BP794 BP795 BP796 BP797 BP798

KEYWORD

hard, nice, abstract, dual, handed, leftright, solved, meta (see left/right), miniproblems, creativeexamples, presentationmatters, assumesfamiliarity, structure, experimental

WORLD

boxes_bpimage_sorts_self [smaller | same | bigger]
zoom in left (boxes_bpimage_sorts_self_left) | zoom in right (boxes_bpimage_sorts_self_right)

AUTHOR

Aaron David Fairbanks

BP795 Image of a Bongard Problem that would sort itself on its own right versus image of a Bongard Problem that would sort itself on its own left.
(edit; present; nest [left/right]; search; history)
COMMENTS

"BONGARD HELL."

This the flipped version of BP793 but using only images of Bongard Problems with solution "__ half more black/less white than other half versus vice versa," that all use rotated, reflected, and inverted versions of the same examples.

CROSSREFS

See BP971 (left vs. right more black) and BP972 (top vs. bottom more black).

Adjacent-numbered pages:
BP790 BP791 BP792 BP793 BP794  *  BP796 BP797 BP798 BP799 BP800

KEYWORD

hard, nice, abstract, dual, handed, leftright, meta (see left/right), miniproblems, presentationmatters, left-finite, right-finite, assumesfamiliarity, structure, experimental, funny

WORLD

bongard_hell [smaller | same | bigger]
zoom in left | zoom in right

AUTHOR

Aaron David Fairbanks

BP796 Image of a Bongard Problem that would sort a blank panel on its left versus image of a Bongard Problem that would sort a blank panel on its right.
(edit; present; nest [left/right]; search; history)
CROSSREFS

See BP567 for the version with links to pages on the OEBP instead of images of Bongard Problems (miniproblems).

Adjacent-numbered pages:
BP791 BP792 BP793 BP794 BP795  *  BP797 BP798 BP799 BP800 BP801

KEYWORD

hard, nice, abstract, dual, handed, leftright, challenge, meta (see left/right), miniproblems, creativeexamples, assumesfamiliarity, structure, presentationinvariant

WORLD

boxes_bpimage [smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

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