Crossing
When two lines disappear behind a mask, the mind fills the gap. That fill is often a little bent, a close cousin of the Poggendorff effect, and the imagined crossing drifts. Short stubs make it worse: the eye starts listening to the mask’s edges instead of the true directions.
Stretch
Bent paths look shorter than they are. Turns seem to spend length. The only honest comparison is to straighten the path and lay it on your bar — which is exactly what the reveal does.
Vanish
A hallway’s top edge and bottom edge must aim at the same point. A strong floor grid often pulls that point down, and an offset room pulls guesses back toward the center of the frame.
Between
On a single interval, people often tap a little early. The midpoint is a moment, not a feeling of ‘about now’. The flashes are the whole cue: the game is playable with the sound off, and the timing does not change if you mute it.
Aftertone
A gray patch on a bright field looks darker than the same gray on a dim field. That is simultaneous contrast. Matching what you remember often means compensating for the surround — and overshooting the true lightness.