Domain: Healthcare — Human Physiology
Target concept: Capillary Refill After Pressure Application on Human Nails

Video generation prompt: Close-up shot: A human finger exerts pressure on the center of another finger's nail for several seconds before releasing.

Evaluation guide:
(i) Target concept: Capillary refill time as a clinical indicator of peripheral perfusion.
Minimum mechanism: Intact microvasculature beneath nail plate; functional arteriolar tone; sufficient cardiac output to drive rapid reperfusion; no external compression or vasoconstriction confounders.
(ii)Storyline: [Frame 0–t1] Baseline: subject nail shows normal pink/rose hue; actor finger approaches but does not yet contact. [t1] Contact onset: actor fingertip touches center of nail → instantaneous pallor onset across nail bed. [t1–t2] Sustained pressure: pallor maintained uniformly; no motion or leakage of color. [t2] Release onset: actor finger lifts away → refill wave initiates precisely at contact point (center). [t2–t3] Refill propagation: color advances continuously and symmetrically toward nail margins. [t3] Completion: entire nail bed restored to identical baseline hue/saturation. Perspective: fixed close-up, frontal view, shallow depth of field emphasizing nail bed; no occlusion; consistent ambient lighting.

Manual:
Experimental Procedure
1. Position two human fingers side-by-side in stable close-up frame: one as actor (exerting pressure), one as subject (bearing pressure on nail).
2. Actor finger presses firmly and steadily onto the exact center of subject finger"s nail for sustained contact.
3. Actor finger releases pressure completely and immediately.
Observation of Experimental Phenomena
- During pressure: nail bed becomes pale/white (pallor).
- Immediately after release: color returns as a visible wave spreading outward from the center of the nail.
Summary of Experimental Principles
Capillary refill reflects microvascular perfusion: pressure displaces blood from nail bed capillaries → pallor; release allows rapid reperfusion → centripetal color return. Delayed or absent refill indicates impaired circulation.

Prompt Grounding rubric:
level_1: No human finger present; or no nail visible; or no pressure application observed; or no release event shown; or subject is not a human finger (e.g., prosthetic, animal, or non-biological object); or shot is not close-up (e.g., full hand, arm, or distant view).
level_2: Human finger and nail are present, but pressure is not applied to the center of the nail (e.g., applied to cuticle, skin beside nail, or fingertip pad); or pressure and release occur without any discernible contact between two fingers (e.g., same finger pressing itself, or finger pressing surface); or release is absent or visually indistinguishable from baseline.
level_3: Two human fingers are present in frame; one finger (actor) makes clear, sustained contact with the center of the other finger's (subject) nail; release occurs after contact; shot is close-up framing the nail and contacting fingertip; all core objects and actions from posted_prompt appear.
level_4: All conditions for score 3 are met, AND the actor finger remains stationary during pressure application (no sliding, lifting, or repositioning before release); AND the subject finger remains motionless (no withdrawal, rotation, or flexion) throughout the entire sequence; AND both fingers maintain consistent spatial relationship (no relative zoom, pan, or re-framing that breaks fixed viewpoint).
level_5: All conditions for score 4 are met, AND the contact area is exclusively the center of the nail plate (not overlapping nail margin or surrounding tissue); AND both fingers are fully visible, unoccluded, and in sharp focus throughout; AND no extraneous objects (e.g., gloves, jewelry, tools, labels) enter the frame at any time.

Scientific and Causal Correctness rubric:
level_1: No observable color change in the nail bed before/during/after pressure; or nail appears uniformly white, black, or opaque throughout; or color change occurs in wrong location (e.g., only skin around nail, not under nail); or color change persists identically before and after release (no transient pallor followed by refill).
level_2: Nail bed shows color change, but it is inconsistent with capillary refill physiology: e.g., immediate full return (no delay), or color deepens instead of lightens under pressure, or refill spreads from edge instead of center, or refill is uniform across entire nail without visible wavefront progression.
level_3: Nail bed visibly lightens (pallor) during pressure application; after release, a distinct wave of color return (refill) begins at the center of the nail and propagates outward; refill completes within the video duration (no partial or stalled refill); color returns to baseline appearance (same hue/saturation as pre-pressure).
level_4: All conditions for score 3 are met, AND pallor is confined to the nail bed (not extending into surrounding skin or cuticle); AND refill wavefront is continuous and unbroken (no skipping, patchiness, or branching); AND no abnormal discoloration (e.g., cyanosis, erythema, yellowing) appears before, during, or after the event.
level_5: All conditions for score 4 are met, AND the nail bed visibly pales as soon as the actor finger presses down, with no slow fade into pallor; AND the color-return wave visibly starts within about one second of the actor finger lifting away, with no noticeable delay between release and the start of refill; AND the refill wave moves steadily from the center toward the nail's edges at a roughly constant pace, without visibly speeding up or slowing down partway through; AND once refill finishes, the nail bed's color closely matches its appearance before the pressure was applied, across the whole nail.

Spatiotemporal Consistency rubric:
level_1: Fingers appear or disappear abruptly rather than entering or leaving the frame by moving; or the nail's shape visibly warps, stretches, or melts; or lighting changes discontinuously (e.g., a flash, strobe, or sudden shadow jump); or the finger's structure breaks in an impossible way (e.g., the nail separates from the fingertip, or a joint bends backward); or the motion is visibly jerky, with repeated freezes or stutters in the fingers' movement.
level_2: Minor structural inconsistency: e.g., the nail's shape changes between shots (bulging or collapsing), the finger's orientation shifts for no reason (e.g., an unexplained rotation mid-contact), the contact point drifts sideways during pressure without a visible repositioning motion, or the shadow cast by the fingers shifts in a way that doesn't match a fixed light source.
level_3: The finger and nail form one continuous, intact structure throughout the shot — no part of the fingertip or nail disappears, splits apart, or bends unnaturally; the ambient light on the nail bed doesn't shift in brightness or color between the pressure and release phases, and any shadow moves only as the fingers themselves move; the actor finger's press-and-release action and the subject finger's stillness both look mechanically natural.
level_4: All conditions for score 3 are met, AND the nail and skin's texture and shininess stay consistent (no sudden shift from glossy to matte or back); AND depth ordering stays consistent (e.g., the fingertip never appears to pass behind the nail and then back in front of it inconsistently); AND the fingers' movement speed changes smoothly, without abrupt starts or stops except at the two defined action moments (contact and release).
level_5: All conditions for score 4 are met, AND inter-finger distance changes monotonically: decreases continuously until contact, holds constant during pressure, increases continuously after release; AND no parallax violation (e.g., background elements shift inconsistently with camera motion); AND no motion blur inconsistent with speed (e.g., static contact showing heavy blur, or fast release showing zero blur).