Motifs
Candidate shapes and candidate clocks for the thing the group makes copies of — prototyped side by side, and measured.
A motif has to do two jobs at once, and they pull against each other. It must carry orientation: a rotated copy has to look rotated and a reflected copy has to look reflected, so the shape can have no symmetry of its own, and its handedness has to survive down to a thumbnail. And it must carry phase: a copy's place in the loop has to be readable from a frozen frame, which asks the clock to be one-to-one over the period, continuous through t = 0 so the loop has no seam, and — the rule that cost the site its first motif — not a rotation, because a turning marker inside a pattern with turning symmetry aliases against the pattern and stops being readable at all.
So a candidate is a shape paired with a channel, and the two are separable: any shape below can carry any channel. The four numbers under each card are measured from the pixels, not asserted — each motif is rasterised at sixteen instants and compared against its own mirror, its own rotations, and its other instants.
handedness — how far the motif is from its mirror image; higher is better, and anything near zero cannot show a reflection. phase — the smallest difference between any two instants of the loop; higher is better, and zero means a frozen frame cannot tell those two instants apart. rotation — the worst similarity to itself turned by 60°, 90°, 120° or 180°; lower is better, since a high score is exactly the aliasing that makes a motif unreadable inside a gyration. seam — the jump across t = 0; lower is better.
Test it against a group
Every card runs the same spacetime group, so the candidates are compared under identical strain. Pick a harder one and watch which motifs stop being readable.
Notes on the sources
The comma is the site's incumbent and the baseline every other candidate is measured against. The letter R is the classic asymmetric test glyph: unlike an abstract shape, a mirrored R is one a reader already knows is wrong, which is what makes it a good handedness marker — and the growing-and-shrinking R is here in two forms, alone and paired with a wipe, because size on its own is a there-and-back and cannot distinguish the two halves of the period.
The flag, the scalene triangle and the bevelled L are in the spirit of the devices Conway, Burgiel and Goodman-Strauss use in The Symmetries of Things to make a pattern's symmetry visible: a shape with a distinguished spine to read a reflection against, a triangle no rotation fixes, and the polyomino pair that is the textbook example of two shapes no turn can identify. They are adaptations for this purpose rather than reproductions of any plate.