Domain: Healthcare — Skin Physiology
Target concept: Sebum Composition Analysis (Sudan III Staining Method)

Video generation prompt: Use clean glass slides, sterile cotton swabs, Sudan III staining solution, pipettes, and a microscope. Gently collect a skin surface sample with a cotton swab, spread it on a glass slide, air-dry, then add Sudan III staining solution. After a brief incubation period, gently rinse and remove excess liquid. Observe under low to medium magnification with a microscope. The entire procedure is continuous and simplified.

Evaluation guide:
(i) Target concept: Visualization of lipid-rich sebum via selective histological staining.
Minimum mechanism: Sudan III must remain soluble in lipid phase but insoluble in aqueous phase; air-drying must fix lipids to slide; rinsing must remove unbound dye without dissolving stained lipids; microscope magnification must resolve globular morphology.
(ii)Storyline: [Skin contact] → [Sample transfer to slide] → [Air-drying (implied dry appearance)] → [Sudan III application] → [Incubation (liquid dwell time visible)] → [Gentle rinse (directional flow, no pooling)] → [Excess removal (no residual film)] → [Microscope positioning] → [Low-to-medium magnification view revealing orange-red globules against unstained background]; all events occur from fixed frontal viewpoint with consistent lighting, no off-screen actions, and no object teleportation.

Manual:
Experimental Procedure
1. Gently rub sterile cotton swab on skin surface.
2. Spread swab material onto clean glass slide; air-dry.
3. Apply Sudan III staining solution using pipette.
4. Rinse gently; remove excess liquid.
5. Observe stained sample under microscope (low-medium magnification).
Observation of Experimental Phenomena
Discrete orange-red globules appear on slide after staining and rinsing, visible under microscope against pale background — no uniform red film or background staining.
Summary of Experimental Principles
Sudan III selectively binds to lipids (e.g., sebum triglycerides); stained lipids appear as distinct orange-red droplets, confirming sebum presence on skin surface.

Prompt Grounding rubric:
level_1: No clean glass slide, no sterile cotton swab, no Sudan III staining solution, no pipette, no microscope visible; or none of the five core tools/materials appear at any time.
level_2: At least one of the five required items appears (glass slide, cotton swab, Sudan III solution, pipette, microscope), but fewer than three are present; or all five appear but in unrelated contexts (e.g., microscope shown alone on desk without sample, Sudan III bottle shown without application).
level_3: All five required items appear: clean glass slide, sterile cotton swab, Sudan III staining solution (in container), pipette (used or held), and microscope (in use or clearly positioned for observation); however, at least one critical action is missing (e.g., swab never contacts skin surface, or slide never receives sample, or staining solution never dispensed onto slide, or microscope never shows view of slide).
level_4: All five required items appear AND all four critical actions occur in correct sequence: (1) cotton swab contacts skin surface, (2) swab transfers material to glass slide, (3) pipette dispenses Sudan III solution onto slide, (4) microscope is used to observe slide; but one non-core flaw exists (e.g., pipette tip touches slide surface instead of dispensing above; or swab is reused visibly; or microscope focus adjustment shown but no view displayed).
level_5: All five required items appear AND all four critical actions occur in correct sequence with correct spatial relationships: (1) cotton swab contacts skin surface (visible contact zone), (2) swab is swept across clean glass slide to deposit sample (visible transfer and spread), (3) pipette dispenses Sudan III solution directly onto deposited area (no spill outside slide, no contact between pipette tip and slide surface), (4) microscope eyepiece or monitor displays a view consistent with low-to-medium magnification of stained sample, all within a single continuous scene with fixed viewpoint.

Scientific and Causal Correctness rubric:
level_1: No color change occurs anywhere; or Sudan III solution is applied but no orange-red staining appears; or orange-red appears without Sudan III application; or sample appears fully transparent or black before/after staining with no lipid-specific contrast.
level_2: Sudan III solution is applied, but staining appears only as uniform red/pink wash with no localized orange-red droplets or globules; or orange-red appears but on non-lipid objects (e.g., swab fibers, pipette tip, background); or staining appears before solution application.
level_3: Orange-red staining appears exclusively on the glass slide after Sudan III application, localized to discrete globular or irregularly shaped regions (not uniform film); however, either (a) no unstained baseline is shown (i.e., slide appears pre-stained or pre-colored), or (b) staining persists identically before and after rinsing step (no selective retention), or (c) microscope view shows no contrast between stained and unstained areas.
level_4: Orange-red staining appears exclusively on slide after Sudan III application and rinsing, localized to discrete globular/irregular shapes; staining is absent from swab, pipette, and surrounding slide area; microscope view shows heterogeneous field with orange-red structures against pale yellow/buff background, but either (a) no air-drying step is visually implied (slide appears wet during staining), or (b) rinsing motion is shown but no visible removal of excess liquid, or (c) stained structures lack granular texture under magnification (appears smooth/smeared).
level_5: All causal conditions satisfied: (1) slide is visibly dry before staining (no meniscus, no sheen), (2) Sudan III solution is applied and remains on slide for observable duration (no immediate runoff), (3) gentle rinse removes unbound dye (no residual red film outside stained globules), (4) post-rinse slide shows only discrete orange-red globules (not smears or films), (5) microscope view confirms orange-red globules with defined edges and granular internal texture against non-stained background; no false positives (e.g., dust, scratches) mimic lipid staining.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: e.g., cotton swab appears on slide before appearing on skin; Sudan III solution appears on slide before pipette is shown; microscope view appears before slide is prepared; or abrupt jump cuts between unrelated locations/scenes with inconsistent lighting/background.
level_2: Moderate rupture: e.g., slide appears dry then suddenly glistening (no drying phase shown), or pipette dispenses while swab is still on skin (no temporal separation), or microscope view shows high-magnification detail before low/medium magnification context is established, but all objects remain physically plausible in shape and position.
level_3: Minor continuity flaws: e.g., swab reappears in hand after deposition without visible return motion; pipette hovers over slide then instantly contacts surface (no descent motion); rinse water appears without source or direction; microscope focus changes without corresponding visual shift in image, but all objects maintain consistent size, orientation, and relative placement throughout.
level_4: All objects maintain fixed spatial relationship: slide remains centered in frame; swab moves only between skin and slide; pipette moves only between Sudan III container and slide; microscope remains stationary with consistent angle; lighting, shadow, and background show no abrupt shifts; only one minor flaw: e.g., brief occlusion of slide during rinse with no loss of spatial reference, or momentary defocus during transition to microscope view that recovers within same shot.
level_5: Zero spatiotemporal violations: (1) continuous unbroken shot or seamless cuts preserving exact slide position, lighting, and background; (2) all motions are physically plausible (swab lifts cleanly, pipette dispenses without splash, rinse flows directionally, microscope focus adjusts smoothly); (3) no object flickers, warps, or changes scale; (4) no lighting/shadow discontinuity; (5) all transitions preserve spatial memory (e.g., slide location unchanged before/after rinse, microscope eyepiece aligned with same slide region).