Domain: Healthcare — Microbiology-Immunology
Target concept: TB Detection (Simplified Acid-Fast Staining)

Video generation prompt: Prepare a sputum smear containing Mycobacterium tuberculosis on a glass slide, air-dry, and heat-fix. Cover the smear with carbol fuchsin stain and gently heat. Rinse with water, decolorize with acid-alcohol, rinse again, counterstain with methylene blue, wash, dry, and examine under a microscope.

Evaluation guide:
(i) Target concept: Acid-fast staining enables selective visualization of Mycobacterium tuberculosis bacilli via differential dye retention based on cell wall lipid composition.
Minimum mechanism: Carbol fuchsin must penetrate the waxy cell wall under heat; acid-alcohol must decolorize non-acid-fast material while leaving red dye bound in acid-fast rods; methylene blue must stain the decolorized background without overwriting the red rods.
(ii) Storyline: [Phase 1: Preparation] Sputum specimen deposited on slide → spread into a thin smear → air-drying (loss of wet sheen) → heat-fixing (slide passes through the flame zone three times with no smoke or charring). [Phase 2: Staining] Carbol fuchsin applied → gently heated until faint steam appears → water rinse removes excess dye → acid-alcohol applied → background red fades while discrete red rods persist → second water rinse removes residual acid-alcohol → methylene blue applied → background turns uniform blue → final rinse and dry. [Phase 3: Observation] Microscope view shows a high-contrast field: slender red rods (length clearly greater than width, straight to gently curved, non-branching) against a homogeneous blue background; no red background residue, no blue rods, no mixed morphology. Perspective: A single fixed overhead or oblique lab-bench camera view holds continuously through Phases 1-2; exactly one camera cut is permitted at the start of Phase 3, switching to a single fixed low-power microscope eyepiece view that itself does not pan, zoom, or change magnification for the remainder of the clip; no other viewpoint changes occur, and no critical action zone (e.g., the slide surface during staining) is ever occluded.

Manual:
Experimental Procedure
1. Place sputum specimen on clean glass slide; spread into thin, even smear.
2. Air-dry completely (no gloss).
3. Heat-fix by passing slide 3x through flame.
4. Flood smear with carbol fuchsin; gently heat until steam rises (do not boil).
5. Rinse with water until runoff is clear.
6. Decolorize with acid-alcohol until runoff is colorless.
7. Rinse with water until runoff is clear.
8. Counterstain with methylene blue for 30 sec; rinse, dry, examine.
Observation of Experimental Phenomena
After decolorization: background is colorless; acid-fast bacilli retain bright red color as slender, straight rods. After counterstain: background turns uniform blue; red rods stand out sharply against blue.
Summary of Experimental Principles
Mycobacterium tuberculosis has waxy mycolic acids in cell wall → resists conventional staining → requires heat-assisted carbol fuchsin penetration → acid-alcohol removes stain from non-acid-fast cells but not acid-fast bacilli → methylene blue provides contrasting background.

Prompt Grounding rubric:
level_1: No part of the acid-fast staining setup is shown: no glass slide, no sputum-like specimen, no carbol fuchsin/acid-alcohol/methylene blue containers, no heat source, and no microscope; the scene instead shows an unrelated activity (e.g., a different lab test, or non-laboratory content) with none of these elements present.
level_2: At least one correct setup element appears (e.g., a glass slide or a stain bottle) but almost none of the required actions occur: no specimen is spread into a smear, no air-drying pause is shown, no heat-fixing pass over a flame occurs, and none of carbol fuchsin, acid-alcohol, or methylene blue is applied to the slide; any actions shown are unrelated to this staining procedure (e.g., the slide is simply wiped or set aside).
level_3: Roughly half of the procedure is shown and individually recognizable (e.g., specimen smeared onto the slide, and either heat-fixing over a flame or carbol fuchsin poured onto the slide), but at least three of the remaining actions (water rinse after carbol fuchsin, acid-alcohol decolorization, water rinse after acid-alcohol, methylene blue counterstain) are missing, or the actions that are shown occur out of the manual's order (e.g., methylene blue applied before acid-alcohol).
level_4: All 8 procedural actions appear in the correct order: (1) specimen smeared onto the slide, (2) air-drying, (3) heat-fixing by passing the slide through a flame, (4) carbol fuchsin poured on and gently heated, (5) water rinse, (6) acid-alcohol poured on, (7) second water rinse, (8) methylene blue poured on; and the slide is subsequently placed under a microscope. No action is skipped or reordered, but one non-critical fidelity flaw is tolerable (e.g., the hand briefly leaves the frame during a rinse, or the flame is held at an unusual angle).
level_5: All 8 procedural actions occur in the exact manual order with unbroken visual continuity: the specimen is smeared thinly on the slide → the smear visibly loses its wet sheen while air-drying → the slide passes through the flame three times with no lingering or charring → carbol fuchsin is poured to fully cover the smear and gentle heating produces faint steam → a water rinse is poured over the slide and drains off → acid-alcohol is poured on and allowed to run off → a second water rinse is poured over the slide → methylene blue is poured on and left briefly → the slide receives a final rinse and is set to dry → the same slide is then transferred to the microscope stage for viewing. No action is omitted, added, or reordered, no reagent or tool appears without first being introduced, and the camera follows the single-cut perspective described in the evaluation guide.

Scientific and Causal Correctness rubric:
level_1: No scientifically valid staining chemistry is demonstrated: carbol fuchsin never produces red color on the smear, acid-alcohol shows no selective effect (either nothing decolorizes, or red disappears entirely including from any bacilli-shaped structures), methylene blue never produces a blue background, and no rod-shaped structures of any color ever appear; colors used are chemically implausible for this stain set (e.g., carbol fuchsin appears green, methylene blue appears red).
level_2: Only one link in the differential-staining causal chain is correct, with the rest missing or wrong: e.g., carbol fuchsin correctly reddens the smear, but acid-alcohol either leaves the whole field red (no decolorization occurs) or strips all red including from any rod-shaped structures (over-decolorization, indistinguishable from a smear containing no acid-fast organisms); or methylene blue is applied but the background never visibly turns blue.
level_3: The overall color endpoints are correct (red carbol fuchsin stage visible, background ends up blue after methylene blue) but the acid-fast-specific detail is wrong or missing: either no distinct red rod-shaped structures survive the acid-alcohol step, or red structures survive but appear as shapeless clumps or granules rather than discrete slender rods, or the background never fully clears of red residue before the methylene blue is applied.
level_4: The full causal chain is correct (carbol fuchsin reddens the smear, acid-alcohol clears red from the background while leaving it only in slender, rod-shaped structures, methylene blue then turns the cleared background blue), with one minor scientific imprecision, such as the surviving red rods being noticeably thicker or more sharply bent than typical M. tuberculosis bacilli, or a faint trace of red residue remaining in a small area of the background.
level_5: The differential-staining chemistry is fully and precisely correct: carbol fuchsin produces uniform red coverage of the smear; acid-alcohol decolorization removes red from the background matrix completely while red is retained exclusively in slender (width clearly less than length), straight-to-gently-curving, non-branching rod-shaped structures consistent with M. tuberculosis bacilli; methylene blue then stains the cleared background a uniform blue with no red bleeding into it; the final microscope field shows multiple (at least 3) clearly resolved red rods standing out against an unambiguous blue background, with no over- or under-decolorization and no color mixing in either the rods or the background.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal breaks specific to this procedure: the slide instantly appears already mounted under the microscope objective without the hand that carried it ever entering frame; or the visible smear pattern on the slide changes shape or size between the heat-fixing shot and the staining shot with no reapplication shown; or a reagent bottle (carbol fuchsin, acid-alcohol, or methylene blue) appears in a hand or on the bench with no prior shot of it being picked up; or the flame used for heat-fixing appears with no visible lighter, burner, or match; or the bench lighting used during smear preparation switches to a dim, reddish staining-room lighting with no lamp, switch, or shade change shown to justify it; or the slide's edge visibly cracks and then appears intact again in a later shot.
level_2: Multiple moderate breaks are present: at least two of the reagent bottles change position on the bench between appearances with no hand shown moving them; the rinse water appears to flow upward off the slide at least once; the flame flickers out and reignites with no visible cause; the shadow cast by a reagent bottle or the slide flips to the opposite side between two consecutive procedural shots with no change in the position of the flame or any lamp; the microscope field shown at the end has a visibly different slide outline or scratch pattern than the slide prepared earlier in the clip.
level_3: Exactly one clear spatiotemporal flaw is present: e.g., the slide's orientation rotates by more than a quarter turn between the heat-fixing shot and the staining shot with no hand visibly repositioning it; or the rinse water begins flowing across the slide before the carbol fuchsin has finished being poured; or the acid-alcohol bottle is shown in frame before any earlier shot introduced it; or the microscope image blurs and then sharpens again with no corresponding hand adjustment of a focus knob visible.
level_4: The slide, the three reagent bottles (carbol fuchsin, acid-alcohol, methylene blue), and the flame source each hold a single, unchanging position relative to one another and to the bench edge whenever visible, moving only when a hand is shown moving them; the rinse water consistently flows downward off the slide; the flame stays lit at a steady size only while heat-fixing is occurring; the microscope view keeps the same field boundaries and a single focal plane for the entire observation phase; at most one small, non-repeating timing mismatch is present (e.g., a brief gap between pouring a reagent and its visible color change).
level_5: No spatiotemporal artifacts of any kind: the slide's position, orientation, and the bench lighting stay constant across Phases 1-2 with only the single permitted camera cut into the fixed low-power microscope eyepiece view for Phase 3, which itself never pans, zooms, or changes magnification; every reagent bottle, the flame source, and the slide are each introduced exactly once and remain continuously visible and unmoved except when a hand is shown carrying them; hand movements while pouring and rinsing are smooth and physically continuous with no jumps or impossible grips; the rinse liquid shows coherent downward flow with no floating droplets or reversed flow; the flame is stable in size only during the heat-fixing action; the whole clip has no repeated shots, freezes, or skipped moments.