Domain: Natural Science — Physics
Target concept: A small ball passes by a strong magnet on a smooth surface, undergoing a curved deflection.

Video generation prompt: On a smooth table, a heavy magnet is fixed at the center; launch a steel ball quickly past the magnet from the left side, and observe the trajectory of the steel ball from directly above.

Evaluation guide:
(i) Target concept: Non-contact magnetic deflection of a moving ferromagnetic object in a static field.
Minimum mechanism: Steel ball must be ferromagnetic (not paramagnetic/diamagnetic); magnet must generate a spatially varying field (stronger near poles); motion must be inertial (no propulsion after launch); surface must be low-friction to isolate magnetic influence from drag.
(ii)Storyline: [Frame 0–2] Ball enters frame from left edge, moving horizontally rightward in straight line; [Frame 3–6] As ball nears magnet center, its trajectory visibly bends continuously toward magnet: curvature intensifies near closest approach; [Frame 7–9] Ball exits magnet influence, path gradually straightens into new direction; all while maintaining top-down visibility, no contact, no magnet movement, and no external forces visible. Perspective must remain fixed and orthogonal; entire event must unfold within single continuous shot without cuts or repositioning.

Manual:
Experimental Procedure
1. Fix a heavy cylindrical or rectangular magnet at the exact center of a smooth, flat, horizontal table surface.
2. From the left edge of the table, launch a small steel ball horizontally toward the right, ensuring initial path passes near (but not through) the magnet.
3. Record from directly above using a fixed, orthogonal camera.
Observation of Experimental Phenomena
The steel ball travels in an initially straight line, then undergoes smooth, continuous, non-contact curvature toward the magnet as it approaches, passing closely beside it before continuing on a new straight-line path diverging from the original — forming a distinct asymmetric arc.
Summary of Experimental Principles
A moving ferromagnetic object (steel ball) experiences a magnetic force when entering the non-uniform field of a stationary permanent magnet. The force is always attractive (for ferromagnets), acts perpendicular to velocity, and increases with proximity — resulting in centripetal-like deflection without contact.

Prompt Grounding rubric:
level_1: No magnet present; no steel ball present; no smooth horizontal surface visible; no left-side launch observed; no top-down viewpoint established.
level_2: At least one of: magnet present but not fixed at center; steel ball present but not launched from left side; smooth surface partially visible but inconsistent (e.g., textured, tilted, or occluded); top-down viewpoint absent or oblique (e.g., angled >15° from vertical).
level_3: All required objects present: heavy magnet fixed at center of smooth horizontal surface, steel ball present, launch origin clearly on left side of surface; top-down viewpoint established and maintained throughout; no extraneous objects obscuring the central region; launch action initiated before deflection begins.
level_4: All conditions for score 3 satisfied, AND magnet is visually distinguishable as heavy (e.g., larger/denser appearance than ball), steel ball is visibly metallic (not plastic/glossy non-ferrous), surface appears uniformly smooth and untextured, and launch direction is horizontally left-to-right relative to magnet center; no perspective warping or parallax artifacts.
level_5: All conditions for score 4 satisfied, AND spatial layout is geometrically coherent: magnet occupies central position with symmetric visual margin to left/right edges; steel ball enters frame fully from left edge (no cut-in mid-motion); entire trajectory from entry to post-deflection remains fully within frame and fully visible; no camera drift, zoom, or rotation; viewpoint remains strictly orthogonal to surface plane.

Scientific and Causal Correctness rubric:
level_1: No deflection observed; ball moves in straight line past magnet; ball stops, bounces, or reverses without curvature; magnet visibly attracts ball directly (e.g., ball veers *into* magnet and sticks or halts on contact).
level_2: Deflection occurs but violates ferromagnetic interaction logic: e.g., ball curves *away* from magnet; curvature is convex outward (opposite expected Lorentz-like path); ball changes color, vanishes, or exhibits non-solid behavior (e.g., melting, stretching, transparency change) during motion.
level_3: Ball follows a continuous curved trajectory that deviates *toward* the magnet (non-contact attraction), with clear change in direction: initial linear path bends smoothly into a non-straight arc passing near (but not touching) the magnet; no contact between ball and magnet occurs.
level_4: All conditions for score 3 satisfied, AND curvature is monotonic and consistent: no abrupt kinks, reversals, or discontinuities in path; ball maintains constant solid appearance (no flicker, transparency, or shape distortion); motion remains forward-directed (no backward motion or hesitation); magnet remains stationary and rigid throughout.
level_5: All conditions for score 4 satisfied, AND the curve is causally tied to proximity: the ball's path stays straight until it is visibly close to the magnet, then bends smoothly toward it; curvature increases steadily as the ball nears its closest approach to the magnet and eases off just as steadily as the ball pulls away, forming one smooth continuous bend with no kink, no reversal, and no sudden speeding up or slowing down that isn't explained by the magnet's pull; consistent with the asymmetric arc described in the setup, the bend is visibly tighter on the approach side nearest the magnet and eases more gradually as the ball recedes on the far side.

Spatiotemporal Consistency rubric:
level_1: The ball vanishes from one point on the table and reappears elsewhere without traveling the space in between; the magnet changes position or rotates on the table; the tabletop surface visibly buckles, ripples, or changes texture partway through the clip; the overhead lighting flashes or shifts abruptly, making the whole scene flash bright then dark.
level_2: The ball's motion is stroboscopic, advancing in at least two visible skips rather than gliding continuously; at some point the ball displaces by more than its own diameter between consecutive frames; the magnet or tabletop shows a visible seam, gap, or floating edge where the geometry doesn't meet cleanly; viewed from directly overhead, the ball's shadow detaches from the ball or sits offset to one side at some point even though the overhead light never moved.
level_3: The ball travels continuously along its path with no teleporting, freezing, or breaking apart; the magnet stays fixed and rigid at the center of the table for the whole clip; the tabletop remains flat and intact; viewed from overhead, the ball's shadow stays roughly beneath the ball throughout rather than detaching or appearing on an inconsistent side; no visible rendering glitches (torn edges, flickering surfaces, or the ball's surface breaking up) interrupt the continuity of the ball or magnet.
level_4: All conditions for score 3 satisfied, AND the ball's heading changes smoothly as it curves past the magnet, with no instantaneous flip in direction; the ball's shadow tracks directly beneath it at every point along the curved path, staying the same size and darkness; the magnet's own shadow stays centered beneath it and unchanged; the ball and magnet appear to sit on the same tabletop plane with matching sharpness (no depth mismatch suggesting one was composited in separately).
level_5: All conditions for score 4 satisfied, AND the ball's shadow moves in lockstep with the ball with no lag or skipped frames; any motion blur on the ball changes gradually with its apparent speed rather than jumping erratically from frame to frame; the curved path itself reads as a single smooth arc with no visible jumps or back-and-forth wobble as it bends toward and then away from the magnet.