Domain: Natural Science — Physics
Target concept: Visible Light Spectrum Color Mixing Experiment (Red + Green)

Video generation prompt: Move the red and green laser sources out of the camera's view while keeping them switched on, adjust the optical path so that the two beams overlap on a white screen, and observe the color in the overlapping region.

Evaluation guide:
(i) Target concept: Additive color mixing of coherent monochromatic light sources in free space onto a diffuse white surface.
Minimum mechanism: Two spatially separated, collimated, spectrally pure (635nm red, 532nm green) light beams must propagate linearly, intersect at a common point on a Lambertian white surface, and stimulate human L/M cone response equivalently to ~570nm monochromatic light.
(ii)Storyline: Frame opens with both laser sources and the white screen in view → the red laser source is moved out of camera view while remaining switched on, its beam still entering the frame from where it exited (hand or mount slides the device out of frame) → the green laser source is moved out of camera view the same way, its beam still entering the frame → red beam travels straight across the frame from one side → green beam travels straight across the frame from the other side → both beams move continuously toward the center of the screen → beams converge and stabilize → a yellow region appears *only* at the intersection → yellow persists while the beams remain overlapped → yellow vanishes if either beam deflects → entire sequence observed from a fixed frontal viewpoint with the screen filling the central composition; no camera motion, no cutaways, no secondary angles.

Manual:
Experimental Procedure
1. Move the red and green laser sources out of the camera's view, keeping both switched on and aimed so their beams still enter the frame.
2. Adjust the optical path so the red and green laser beams converge onto the same region of the white screen.
3. Observe the overlapping region on the screen.
Observation of Experimental Phenomena
A single contiguous yellow region appears exclusively where the red and green beams overlap on the white screen; no yellow appears outside the overlap; the red and green beams remain distinct outside the overlap.
Summary of Experimental Principles
Red and green light are additive primary colors; their superposition produces yellow via additive color mixing in the visible spectrum.

Prompt Grounding rubric:
level_1: No white screen is shown, no laser beams enter the frame, and/or the red or green laser device itself remains visibly present in the shot rather than being moved out of camera view; also scored here if only unrelated colored lights (not laser beams) appear.
level_2: A white screen is visible and at least one laser device has been moved out of camera view, but only one beam (red or green) is shown entering the frame, or a laser housing is still visible in the shot, or a beam is shown with no screen present at all.
level_3: Both the red and green laser housings have been moved out of camera view (only their beams are visible, not the devices themselves), a white screen is visible, and both beams are shown traveling toward the screen and meeting there; but the region where they meet is off-center or hard to distinguish from the rest of the screen.
level_4: All of 3-score, plus: the white screen fills the central part of the frame, the red beam enters from one side of the frame and the green beam enters from the other side, and the two beams converge onto a single, clearly bounded patch near the center of the screen, all captured in one continuous shot without cuts.
level_5: All of 4-score, plus: the red beam consistently enters from the left edge of the frame and the green beam consistently enters from the right edge; no extra lamps, reflections, or stray beams appear anywhere in the shot; and the screen surface outside the overlap patch stays plain white for the entire shot.

Scientific and Causal Correctness rubric:
level_1: The overlap region shows a color other than yellow (e.g., orange, brown, gray, magenta, or white); or the region where the beams cross shows red and green as visibly separate patches rather than one blended color; or a yellow patch appears somewhere without both beams actually reaching that spot.
level_2: A yellow patch appears at the crossing point, but red or green light is still visibly unmixed right inside that patch; or the yellow appears before both beams have reached the screen; or more than one disconnected yellow patch appears instead of a single merged region.
level_3: Both beams are visibly present and reach the screen, and a single, connected yellow patch forms only where they cross; but the patch looks noticeably greenish or reddish rather than a clean yellow, or it is fringed by a wide unmixed red or green halo more noticeable than the yellow itself.
level_4: The overlap patch reads as a clean, even yellow with no obvious red or green tint remaining inside it, appears only at the crossing point, and disappears (reverting to two separate colored spots) if one beam is blocked or steered away, with no other unexpected color such as cyan or magenta appearing anywhere.
level_5: All of 4-score, plus: the yellow patch's brightness looks comparable to the red and green beams beside it (not conspicuously dimmer or washed out), there is no visible colored fringe or halo bleeding from the patch's edge, and when the beams are nudged apart the yellow cleanly separates back into a distinct red spot and a distinct green spot rather than lingering as a smeared blend.

Spatiotemporal Consistency rubric:
level_1: The red or green beam vanishes and reappears at a different position without traveling through the space between; a beam's path suddenly bends or jumps in direction; the white screen changes texture, tilts, or warps mid-shot; or the lighting on the scene changes abruptly with no visible cause.
level_2: Beam paths show noticeable warping or curvature inconsistent with straight-line travel; the screen appears to drift, rotate, or shift in perspective; the point where the beams cross jumps around rather than moving smoothly; or a shadow or highlight on the screen switches side unexpectedly between moments.
level_3: Both beams travel toward the screen along smooth, straight paths at a steady pace, the crossing point moves continuously rather than jumping, and the screen stays flat and fixed, with at most one brief, barely noticeable flicker or hesitation in a beam that does not disrupt the overall sense of continuous motion.
level_4: Beam motion is fully smooth throughout: both beams enter, travel, and converge with steady width and direction, settling at the overlap point without overshoot or visible stutter; the screen shows no warping, no perspective drift, and no lighting change; the spatial relationships between the beams, the crossing point, and the screen stay coherent for the entire shot.
level_5: All of 4-score, plus: beam width and brightness look steady along the full visible path with no noticeable thickening, thinning, or fading; there is no blur so heavy that it obscures the beam edges or overlap boundary; the video shows no stutter, repeated frames, or juddering; and the beams' final convergence happens in one continuous motion with no visible pause or reversal.