Domain: Humanities and Social Sciences — Economics
Target concept: Monopoly demand curve: A downward-sloping curve that coincides with the industry demand curve.

Video generation prompt: Draw the demand curve of a monopolist on a graph, with price on the vertical axis and quantity on the horizontal axis.

Evaluation guide:
Target concept: The monopolist’s demand curve is the industry demand curve, a single, downward-sloping relationship mapping price to quantity demanded across the entire market. Minimum mechanistic assumptions: (1) single seller, (2) no close substitutes, (3) price-maker behavior, (4) ceteris paribus conditions (no external shifts). Phased storyline: (1) Axes materialize: vertical ‘P’, horizontal ‘Q’, correctly oriented; (2) Downward-sloping curve draws smoothly from top-left to bottom-right; (3) Label ‘D’ appears at curve midpoint, followed instantly by equivalence annotation ‘≡ Industry Demand’. Visibility constraints: Must be legible at 720p resolution; no occlusion; all text ≥14pt; curve contrast ≥90% against background; no decorative elements interfering with core triad (axes + curve + equivalence label).

Manual:
I. Basic Demonstration Information
Demonstration Title: Monopoly Demand Curve Demonstration
Subject: Economics - Microeconomics - Market Structures
Demonstration Purpose: To visually construct and verify the monopolist’s demand curve as a downward-sloping line that coincides identically with the industry (market) demand curve; to reinforce that a monopolist is the sole supplier and thus faces the entire market demand schedule; to enable accurate graphical representation with price on vertical axis and quantity on horizontal axis.
II. Demonstration Carrier/Equipment
Core Carrier: Static digital graph (vector-based, high-resolution SVG-style rendering)
Auxiliary Equipment: None — pure schematic diagram; no human operator, no physical tools.
III. Demonstration Content Description
Layout: Centered Cartesian plane occupying ≥70% of frame; vertical axis labeled "Price (P)" with upward arrow; horizontal axis labeled "Quantity (Q)" with rightward arrow; both axes scaled proportionally with evenly spaced ticks (no numeric values required).
State Control: Graph remains static after full rendering; no animation beyond initial construction sequence (axes → curve → label); all elements rendered in high-contrast black on white background.
Comparison Baseline: Not applicable — no comparative curves (e.g., no supply, MR, or competitive demand); sole focus is the identity and shape of the monopoly demand curve.
IV. Observation of Core Phenomena
Axis Orientation & Labeling: Vertical axis unambiguously marked "P" or "Price", horizontal axis "Q" or "Quantity" — orientation matches standard microeconomic convention.
Curve Shape: Single, continuous, smooth, downward-sloping line extending from upper-left quadrant toward lower-right quadrant — no kinks, breaks, or reversals.
Curve Identity: Labeled "D" (or "Monopoly Demand") and explicitly annotated "≡ Industry Demand Curve" (via equal sign or textual equivalence) — confirming the defining theoretical principle.
Visual Stability: No flicker, jitter, distortion, or spatial drift; all elements maintain fixed relative geometry throughout observation.
V. Summary of Key Knowledge Points and Principles
Core Concept Definition: In a monopoly, there is only one seller, so the firm’s demand curve is numerically and functionally identical to the market demand curve — a downward-sloping relationship reflecting the law of demand.
Economic Significance: This identity underpins all monopoly analysis: marginal revenue lies below demand, profit maximization occurs where MR = MC, and deadweight loss arises because P > MC along the demand curve.
Further Knowledge: Unlike competitive markets (where firm demand is horizontal), monopoly demand is downward-sloping *because* the firm *is* the market — no distinction exists between firm-level and industry-level demand schedules.

Prompt Grounding rubric:
level_1: No graph appears, or the axes are absent, mislabeled (e.g., price plotted on the horizontal axis instead of quantity), or reversed in orientation; no continuously downward-sloping line is drawn: the line is flat, upward-sloping, vertical, or broken into disconnected segments; the core visual triad of a price axis, a quantity axis, and a single downward-sloping curve is not recognizably present.
level_2: A two-axis coordinate system is drawn, but at least one axis is mislabeled or unlabeled (e.g., 'Q' placed on the vertical axis, or no axis titles at all); a line is present but is not a smooth downward slope (it zigzags, steps, or stays flat); the line does not span a meaningful range of the plotted area; nothing on screen (no letter 'D', no word 'Demand') indicates the line is meant to be a demand curve.
level_3: The vertical axis is labeled 'Price' (or 'P') and the horizontal axis is labeled 'Quantity' (or 'Q'), correctly oriented; a single, continuous, downward-sloping line runs from the upper-left toward the lower-right of the plot; however, the curve carries no label at all ('D', 'Demand', or 'Monopoly Demand' is missing), and nothing on screen ties the curve to the idea of industry-wide demand; small omissions such as missing arrowheads or tick marks do not affect the correct axis layout and slope.
level_4: Axes are correctly oriented and labeled ('Price'/'P' vertical, 'Quantity'/'Q' horizontal); a smooth, continuous, downward-sloping curve is drawn and occupies the central portion of the plot at a legible scale; the curve carries at least one clear label ('D', 'Monopoly Demand', or 'Industry Demand'); no contradictory curve (e.g., an upward-sloping supply line or a second demand-like curve) appears on the same plot; only cosmetic imperfections remain, such as slightly uneven line weight or a faint tick mark.
level_5: The plot shows bold, correctly oriented axes labeled 'Price (P)' (vertical, arrow pointing up) and 'Quantity (Q)' (horizontal, arrow pointing right); a single, clean, high-contrast curve slopes smoothly from upper-left to lower-right without kinks or breaks; the curve is labeled 'D' or 'Monopoly Demand' near its midpoint; no unrelated shapes, text, or curves share the frame; line weight, spacing, and lettering stay legible and consistent for the whole shot.

Scientific and Causal Correctness rubric:
level_1: The plotted curve is not consistent with the law of demand (it is flat, vertical, or slopes upward), or the video visually contradicts the target claim by showing two separate curves, one for 'the monopolist' and a different one for 'the market'/'industry', implying the monopolist's demand is something narrower than the whole market, which misrepresents a single-seller monopoly.
level_2: A single downward-sloping curve is shown, consistent with the law of demand, but nothing about the video (no label, no caption, no narration) signals that this curve represents the entire market's demand rather than an arbitrary or unspecified relationship; the central claim that a monopolist (the sole seller) faces the whole market's demand is not addressed in any way.
level_3: The downward-sloping curve is labeled as the monopolist's demand (e.g., 'D' or 'Monopoly Demand'), correctly reflecting the law of demand, but its equivalence to the industry/market demand is left implicit: nothing in the visuals explicitly states or shows that this same curve is also the industry demand; a viewer would need outside knowledge of monopoly theory to infer the equivalence.
level_4: The curve is labeled as the monopolist's demand AND a clearly connected visual or textual cue (e.g., an adjoining phrase or annotation near the same curve) states that this curve is also the industry/market demand; only one curve is shown throughout: there is no second, separately labeled 'firm demand' curve that would undercut the single-curve identity claim.
level_5: A single curve carries both identifications together and unambiguously (e.g., a label reading 'D = Industry Demand' or equivalent phrasing appears attached to the one curve), leaving no possibility of reading the monopolist's demand as narrower than, or different from, the whole market's demand; no hedge, qualifier, or competing curve weakens this identity claim.

Spatiotemporal Consistency rubric:
level_1: The graph's elements build up out of order or inconsistently: for example the curve appears before the axes are finished, or elements pop in and out unpredictably; the camera view itself is unstable, zooming, panning, or rotating rather than holding a fixed shot of the plot.
level_2: Axes and curve appear, but with visibly mismatched styling between them (e.g., the axes are drawn crisply while the curve is drawn in a different weight or color); the curve's drawing motion stutters or pauses rather than flowing continuously; any label appears after a distracting delay or in a mismatched font; the overall framing drifts or wobbles slightly rather than holding steady.
level_3: The plot stays centered and steady in the frame for the whole clip; both axes are drawn together with matching stroke weight and color; the demand curve is drawn in one smooth, continuous motion from one end to the other; its label appears shortly after the curve finishes, without flicker or repositioning; small cosmetic roughness (e.g., a slightly tapered line end) does not affect legibility.
level_4: In addition to the above, the axes and curve keep a uniform, crisp line weight and color for the entire clip with no thickening, thinning, or color drift over time; the curve is drawn at a roughly constant speed from start to finish; the frame never zooms, pans, or rotates; the build-up order (axes, then curve, then label) is never reversed or overlapped.
level_5: The whole sequence holds together with no noticeable timing or positional slips: the plot's size, position, and framing stay fixed for the entire duration; the curve is drawn at an even pace in one unbroken stroke; the equivalence label appears promptly, stays legible, and does not move once shown; stroke quality, curve path, and label placement look the same at the end of the clip as they did when each element first appeared.