Domain: Natural Science — Physics
Target concept: The ferrofluid initially exhibits a uniform state, forming a spiky structure near the magnet.

Video generation prompt: A shallow and transparent container filled with black ferrofluid is placed above a vertical platform, beneath which a strong circular magnet is slowly rising upward from below toward the container.

Evaluation guide:
(i) Target concept: Magnetic field gradient-induced normal-field instability in ferrofluids.
Minimum mechanism: Ferrofluid must be a stable colloidal suspension (not sedimented or phase-separated); magnet must generate a non-uniform vertical field with increasing gradient near its pole; container must be non-magnetic and optically transparent to observe surface deformation.
(ii)Storyline: Frame 0–2: Uniform flat black liquid surface visible in shallow transparent container on rigid vertical platform; circular magnet fully hidden beneath platform, no visible influence. Frame 3–6: Magnet begins upward motion (spiky protrusions emerge *only* at container bottom region aligned with magnet center); spike count and height increase continuously with magnet ascent. Frame 7–9: Magnet reaches closest position (spikes maximally developed, symmetric, and stable); no lateral spread beyond magnet projection. Frame 10: Motion stops, spikes collapse within one visual interval back to uniform flat state. Perspective: Fixed frontal view, eye-level with container mid-height, no camera motion or focus shift.

Manual:
Experimental Procedure
1. Place a shallow, transparent container filled with black ferrofluid onto a vertical platform.
2. Position a strong circular magnet centered directly beneath the platform.
3. Slowly raise the magnet upward from below until it approaches the underside of the container.
Observation of Experimental Phenomena
The ferrofluid begins in a uniform, flat state; as the magnet rises, a distinct spiky structure emerges exclusively near the bottom surface of the container directly above the magnet.
Summary of Experimental Principles
Ferrofluids are colloidal liquids containing nanoscale magnetic particles; under an external magnetic field gradient, they form peaks (spikes) aligned with field lines — strongest where field gradient is steepest, i.e., near the magnet surface.

Prompt Grounding rubric:
level_1: None of the required objects are visible: no shallow transparent container, no black ferrofluid, no vertical platform, and no cue (visible or implied by camera framing) that anything is approaching the platform from below.
level_2: At least one of the container, ferrofluid, or platform is visible, but the arrangement contradicts the setup: for example the container does not sit on or above the platform, the platform is missing entirely, or there is no depiction of anything moving upward toward the assembly from below.
level_3: The shallow transparent container filled with black ferrofluid sits on the vertical platform, and the platform fully occludes whatever lies beneath it, but there is no visible motion of anything moving upward toward the platform: the platform itself never shifts, and no accompanying motion cue (vibration, framing change, etc.) suggests anything is rising.
level_4: All setup elements are correctly arranged: the shallow transparent container (visibly shallow, showing the fluid surface and container edges clearly) holds the black ferrofluid and sits on the rigid vertical platform; the platform stays opaque and continuously hides whatever is beneath it; something is depicted approaching upward from below the platform toward the container; however, the occlusion briefly breaks (a flicker or partial peek beneath the platform) or the upward approach is not fully continuous (a jump or pause interrupts the motion).
level_5: Beyond what is required for score 4, the platform's occlusion of whatever is rising beneath it is total and unbroken from the first moment to the last (no flicker, gap, or partial reveal at any point); the upward approach toward the container is smooth and continuous with no lateral drift, no jump cuts, and no change in camera viewpoint; the container, platform, and ferrofluid never shift position relative to one another at any point in the clip.

Scientific and Causal Correctness rubric:
level_1: The fluid shown is not black, or does not behave as a liquid (it looks solid, granular, or metallic-solid); no spiky structure ever appears near the platform; if an upward motion beneath the platform is shown, it produces no visible response in the fluid at all.
level_2: The fluid is black and liquid-like, but its surface stays flat or only shows random ripples/bubbles unrelated to any upward motion beneath it; a spiky structure never appears; or if spikes do appear, they show up with no corresponding upward motion beneath the platform, or they persist even after that motion has stopped.
level_3: The fluid starts flat and, as the magnet rises beneath the platform, spikes begin to emerge on the container's bottom surface; but the spikes are sparse, appear off-center, vanish before the magnet reaches its highest point, or linger noticeably after the magnet has stopped moving; the link between the magnet's rise and the spikes is present but weak or inconsistent.
level_4: Ferrofluid begins fully uniform and flat; spikes appear only near the region of the container bottom directly above the rising magnet, growing in number and height as the magnet continues to ascend; all spikes disappear soon after the magnet stops moving; but one of the following occurs: (a) a few spikes appear before the magnet has started rising, (b) the spikes form asymmetrically even though the magnet is centered, or (c) the flat, spike-free starting state is not clearly shown before the magnet begins to move.
level_5: Ferrofluid is visibly flat and spike-free in the opening moments, before the magnet begins rising; once the magnet starts moving, no spikes appear until it has drawn close enough beneath the container; a delay after motion starts is expected and scientifically correct, since the instability only triggers once the field gradient is strong enough, so spikes are not required to begin the instant the magnet starts moving; once they do begin, spikes appear only in the area of the container bottom aligned with the magnet's center and grow in number and height as the magnet keeps ascending; all spikes disappear within roughly a second after the magnet stops moving; no extraneous droplets, splashes, or swirls appear at any point; the fluid stays uniformly black throughout.

Spatiotemporal Consistency rubric:
level_1: The container jumps abruptly to a different position with no motion shown connecting the two positions; whatever is beneath the platform appears or disappears with no visible motion; the ferrofluid surface flickers wildly or appears to break into disconnected chunks; the lighting flips from full shadow to full brightness (or the reverse) between consecutive shots; the platform or container edges warp or dissolve at some point.
level_2: The container visibly wobbles or tilts for no physical reason; the upward-moving element beneath the platform advances in noticeable jerky jumps rather than smooth continuous motion; the fluid's spikes blink on and off inconsistently rather than growing or shrinking smoothly; a shadow detaches from its object or suddenly points a different direction than the light source; the camera view rotates or zooms without any clear reason.
level_3: The container shows a barely perceptible sideways drift rather than staying perfectly still; the upward motion beneath the platform briefly pauses and then resumes in the same direction rather than moving perfectly smoothly; the fluid surface shows a faint tremor or ripple unrelated to the spike formation; shadow softness shifts gradually in a way that doesn't quite match a fixed light source, though nothing breaks continuity outright.
level_4: The container and platform never shift relative to each other and keep the same shape from start to finish; the upward motion is smooth and continuous with no visible stutter, jump, or warping; the lighting and the shadows cast by the container and platform look the same in direction, brightness, and softness from start to finish; nothing on screen flickers, tears, or deforms, except for one small flaw, such as the container's edge briefly blurring during motion, or the hidden element becoming very briefly and partially visible through the platform when it should be fully occluded.
level_5: The container stays perfectly still and upright for the entire clip; the upward motion beneath the platform is smooth and continuous from start to finish, remaining fully hidden by the platform until the moment of closest approach; the ferrofluid surface's transition between flat and spiky evolves smoothly, with no flicker, tearing, or sudden jump in its shape; the lighting and shadows on the container and platform stay constant in direction, contrast, and softness throughout, with no unexplained shift in brightness or shadow angle at any point.