Domain: Humanities and Social Sciences — Economics
Target concept: Law of Supply: When the price increases, the quantity supplied moves upward along the curve.

Video generation prompt: A coordinate axis is displayed, with the horizontal axis representing quantity supplied and the vertical axis representing price, and a supply curve is plotted. Starting from point A, which corresponds to a lower price and a smaller quantity, point A moves to point B as the price increases. Please indicate the position of point B.

Evaluation guide:
Target Concept: Law of Supply, a positive relationship between price and quantity supplied, holding all else constant (ceteris paribus), manifested as movement *along* a fixed supply curve. Minimum mechanistic assumptions: (i) supply curve is exogenously fixed (no input cost changes, technology shocks, or policy shifts); (ii) price is the sole varying determinant; (iii) producer response is instantaneous and frictionless. Expected Phenomena Storyline: Phase 1 (t=0–2s): Static setup. Labeled axes, upward-sloping supply curve, point A anchored at low-price/low-quantity. Phase 2 (t=2s): Price increase triggered. Visible update of y-axis price label (e.g., $2 → $5). Phase 3 (t=2–2.8s): Causal response. Point A smoothly traverses the supply curve to point B, which must satisfy: (i) same curve, (ii) higher P, (iii) higher Q. Phase 4 (t=2.8s+): Stable endpoint. B highlighted, labeled, and verified on-curve. Visibility constraints: All elements must be legible at 720p resolution; no occlusion; text labels ≥24pt; motion must be discernible within ≤10s total duration; no auditory component required.

Manual:
I. Basic Demonstration Information
Demonstration Title: Law of Supply – Movement Along the Supply Curve Demonstration
Subject: Economics - Microeconomics - Markets and Prices
Demonstration Purpose: To visually demonstrate the Law of Supply — that an increase in price causes a movement *upward along* a given supply curve, resulting in a higher quantity supplied — using a dynamic 2D coordinate graph. Enables learners to distinguish movement along vs. shift of the supply curve, recognize core graphical relationships, and verify causal directionality.

II. Demonstration Carrier/Equipment
Core Carrier: Animated 2D coordinate graph (digital, vector-based rendering)
Auxiliary Equipment: None (self-contained visual simulation)

III. Demonstration Content Description
Layout: Full-screen Cartesian plane with origin at bottom-left. Horizontal axis labeled "Quantity Supplied" (right-pointing arrow), vertical axis labeled "Price" (upward-pointing arrow). Uniform linear scale on both axes (e.g., 0–50 units horizontally, $0–$10 vertically). Upward-sloping straight-line supply curve plotted from (Q=5, P=$1) to (Q=45, P=$9).
State Control: Initial state shows stationary blue dot at point A = (Q=10, P=$2), labeled "A". At t=2s, vertical price label on y-axis animates from "P = $2" to "P = $5" over 0.5s. Concurrently (t=2.0–2.8s), the dot slides smoothly *along the supply curve* to point B = (Q=25, P=$5), where it stops and pulses gently. Point B is labeled "B" in bold red font with a halo effect. A thin gray arrow traces the path from A to B along the curve.
Comparison Baseline: No other curves (e.g., demand), no shifts, no external agents — isolates *ceteris paribus* movement along supply curve.

IV. Observation of Core Phenomena
Expected Phenomenon: As price rises from $2 to $5, the representative point moves *up and right* along the fixed supply curve — confirming quantity supplied increases from 10 to 25 units.
Expected Screen: Clean, minimal graph. Only elements: axes with labels, supply curve, point A (blue, static pre-t=2s), price label update animation, point B (red, appears at t=2.8s), connecting path arrow.
Visual Verification Features: (1) Axes correctly oriented and labeled; (2) Supply curve strictly upward-sloping; (3) Point A and B both lie *on* the curve; (4) B has greater Q-value *and* greater P-value than A; (5) Motion path coincides exactly with curve segment between A and B; (6) Price increase precedes or coincides with motion onset — no reverse causality.

V. Summary of Key Knowledge Points and Principles
Core Concept Definition: The Law of Supply states that, ceteris paribus, producers are willing and able to offer more of a good for sale as its market price rises — reflected graphically as upward movement *along* a stable supply curve.
Principle of Visual Feature Recognition: Correct identification requires verifying *three simultaneous conditions*: (a) axis labeling matches economic convention (Q horizontal, P vertical), (b) curve slope is positive, and (c) movement is constrained to the curve — distinguishing it from a supply curve *shift* (which would require curve relocation).

Prompt Grounding rubric:
level_1: No coordinate axes are drawn, or the axes are unlabeled, or no supply curve appears, or neither point A nor point B is shown, or the price and quantity axis labels are swapped (price on the horizontal axis), or the marked point moves left/down instead of up/right along the curve.
level_2: Axes are drawn but mislabeled (e.g., horizontal axis reads 'Price' or vertical axis reads 'Quantity Supplied'), or the curve is drawn but is flat or downward-sloping instead of upward-sloping, or point A appears at a low price/low quantity but point B is placed with no clear relationship to A (e.g., same price, a lower quantity, or floating off the curve), or there is no visible motion or transition from A to B at all.
level_3: The horizontal axis is labeled 'Quantity Supplied' and the vertical axis is labeled 'Price'; an upward-sloping supply curve is plotted; point A sits at the lower-price, lower-quantity position on the curve; a second point appears further up the same curve at a higher price, but its status as 'point B, reached after the price rose' is ambiguous, since there is no animation, arrow, highlight color, or label distinguishing it as the new point reached after A moved.
level_4: All of score 3 is satisfied AND point A and point B are both clearly marked with distinct, persistent visual identifiers (e.g., different colors or the labels 'A' and 'B') AND a visible transition (an animated dot sliding along the curve, or a directional arrow) connects A to B AND a price-increase cue (e.g., a rising marker or updating value on the price axis) is shown, but its timing relative to the point's motion is not as cleanly established as at the 5-point level (e.g., the cue appears only partway through the motion, or its ordering relative to the motion is a bit unclear).
level_5: All of score 4 is satisfied AND the axes are explicitly labeled 'Quantity Supplied' (horizontal) and 'Price' (vertical) AND point A is shown first at its coordinates, labeled 'A' AND the price increase is shown as a distinct visual event (e.g., a rising marker on the price axis or an updating price value) that occurs before or exactly as the point begins to move AND point B then appears at its new coordinates on the same curve, labeled 'B' and visually highlighted, connected to A by a smooth path that follows the curve itself rather than jumping off it or crossing axes incorrectly.

Scientific and Causal Correctness rubric:
level_1: Point B ends up at a lower quantity than point A despite the price being higher (violating the Law of Supply), or the curve slopes downward, or point B is not actually on the supply curve, or the movement from A to B has no connection to any price change, or the plotted curve behaves like a demand curve (downward-sloping) rather than a supply curve.
level_2: The curve is upward-sloping, but point B sits at the same quantity as A (a purely vertical move) or the same price as A (a purely horizontal move), or a price increase is shown without any accompanying increase in quantity, or the point moves before any price change is shown, or quantity appears to increase first with the price increase following afterward.
level_3: Point B lies on the same supply curve as A, at both a higher price and a higher quantity than A, satisfying the Law of Supply numerically, but nothing in the video signals that the price increase is what causes the movement (no price marker change, no timing cue linking the two); the point's motion could just as easily be read as happening on its own, unconnected to price.
level_4: A price increase is shown as a distinct visual event (e.g., the price value or marker on the vertical axis visibly rises) and the point's movement up along the curve to B visibly follows that price increase, with quantity increasing accordingly; the curve itself stays fixed throughout (it is not redrawn or shifted), correctly showing movement *along* rather than a shift of the curve, but there is no additional visual reinforcement (such as an on-screen note) tying the price rise explicitly to the higher quantity supplied.
level_5: The supply curve never shifts or redraws; a price increase is shown as an unambiguous visual event on the price axis before or as point A begins moving; point A travels only along the existing curve (never leaving it) to reach point B, arriving at a strictly higher price and strictly higher quantity than where it started; and no extra curves, intersections, or shifting elements (e.g., a demand curve, an equilibrium point, a second supply curve) are present to distract from the fact that this is pure movement along a single fixed supply curve.

Spatiotemporal Consistency rubric:
level_1: The axes don't meet at a clear origin or are skewed at an angle, or the curve bends backward or crosses over the axes, or point A or B appears to float outside the plotted axes, or the point jumps instantly from A's location to B's location with no motion in between, or point B appears before point A does, or before any price change is shown.
level_2: The axes are perpendicular and meet at the origin, but the tick spacing is visibly uneven along one axis, or point A and point B look noticeably different in size or boldness from each other, or the point travels in a straight line that cuts across the plot rather than sliding along the curve, or there is a long, clearly noticeable pause between the price changing and the point starting to move.
level_3: The axes are evenly scaled and labeled, and A and B look the same size and style as each other; the point does slide along the curve, but the motion starts or stops abruptly rather than easing in or out, or the point's appearance changes partway through the motion (e.g., its color shifts, or it briefly disappears and reappears), or there is a brief but noticeable pause before the motion begins after the price changes.
level_4: The axes keep a consistent, evenly-spaced scale throughout; the moving point keeps the same size, color, and outline for the entire motion; the slide from A to B is eased (it visibly speeds up then slows down rather than moving at a constant rate) and stays on the curve the whole way; the point begins moving at essentially the same moment the price change is shown, with no noticeable frame drops, flicker, or warping of the curve's shape.
level_5: The axes meet at a clean right angle at the origin with positive directions running right and up; the supply curve rises smoothly with no backward bends or kinks; point A turns into point B through one continuous slide that never leaves the curve, keeping the same shape, color, and outline the whole way; the price-axis change and the start of the point's motion happen at essentially the same moment and the motion ends cleanly at B's position; and the axes, curve, and points hold their shape and framing throughout the clip: no zooming, tilting, or perspective shift changes how the graph looks from one moment to the next.