Domain: Natural Science — Astrophysics & Astronomy
Target concept: The star undergoes uniform expansion in volume, with a continuous color transition from yellow-white to orange-red, and no abrupt change in brightness.

Video generation prompt: Display the time-lapse process of a solar-type star as it evolves through its later-life stage after leaving the main sequence, keeping the star as the sole subject in a fixed, unobstructed camera view for the whole sequence.

Evaluation guide:
(i) Target concept: Stellar evolution from main sequence to red giant phase, governed by core contraction / envelope expansion thermodynamics.
Minimum mechanism: Radiative energy transport must remain dominant (no convection-driven surface chaos); photospheric opacity increase must drive adiabatic cooling; radius increase must dominate over temperature decrease to preserve near-constant bolometric luminosity.
(ii)Storyline: Frame 1–2: Compact yellow-white star, sharply defined, high surface temperature appearance. Frame 3–5: Star begins smooth radial expansion; hue warms progressively to pale orange. Frame 6–8: Expansion continues visibly; color deepens to saturated orange. Frame 9–10: Star reaches largest apparent size with unambiguous orange-red hue; surface remains uniformly luminous, no granulation or flaring; viewpoint fixed, no background motion; all transitions continuous and synchronous.

Manual:
Experimental Procedure
1. Begin with a single, compact, luminous yellow-white circular object representing a main-sequence star.
2. Gradually increase its diameter while simultaneously shifting its dominant hue along the warm spectrum: yellow-white → pale yellow-orange → deep orange → orange-red.
3. Maintain constant apparent brightness and fixed central position throughout.
Observation of Experimental Phenomena
A single star-like object expands continuously in size and transitions smoothly in color from yellow-white to orange-red, with no flicker, jump, split, or brightness change.
Summary of Experimental Principles
A solar-type star evolving off the main sequence expands uniformly as hydrogen fusion ceases in its core; cooling surface temperature causes observed color shift from yellow-white to orange-red, while luminosity remains approximately constant during early red giant branch ascent.

Prompt Grounding rubric:
level_1: No star-like object appears at all, or several disconnected star objects appear instead of one, or the star is missing for most of the clip, or something other than the star (e.g., on-screen text, other bodies) dominates the frame.
level_2: A single star object is present, but it appears only briefly or only in part of the clip (e.g., only in the final frame with no earlier appearance), or other objects, planets, or background elements compete for visual attention with the star.
level_3: A single, self-contained glowing star sits alone in the frame as the only subject for the entire clip; no other planets, spacecraft, text overlays, or distracting objects appear; the star stays roughly centered in the shot the whole time.
level_4: Everything in score 3 holds, and in addition the star's silhouette stays one continuous rounded shape throughout (never splitting apart, flattening into an odd shape, or being cut off by the frame edge); the camera's framing and distance to the star stay the same, with no re-centering or reframing partway through.
level_5: Everything in score 4 holds, and in addition the background behind the star (dark space, with or without faint background stars) stays visually unchanged throughout, and the star is never partly hidden or clipped by the edges of the frame at any point in the clip.

Scientific and Causal Correctness rubric:
level_1: The star's color changes in a way that contradicts real stellar aging (for example it turns blue, green, or purple instead of warming in hue), or the color shifts backward from orange-red toward yellow-white, or the color change happens before any growth in size is visible.
level_2: The star grows larger but its color never shifts from its starting shade, or its color shifts on schedule but the star doesn't visibly grow (or even shrinks) at the same time, or the star reaches a fully orange-red color before it has grown at all.
level_3: The star continuously grows in apparent size while its color shifts from yellow-white toward orange-red, with the reddest color appearing once the star has reached its largest size in the clip; growth and reddening proceed together in the right order; no physically implausible star colors (magenta, cyan, or flat gray) appear at any point.
level_4: Everything in score 3 holds, and in addition the color keeps trending warmer without ever swinging back toward the cooler starting shade; the star's size keeps increasing without shrinking or pulsing back down; there is no sudden dimming or flare-up in the star's overall brightness that would be unrelated to its gradual aging.
level_5: Everything in score 4 holds, and in addition the color looks evenly applied across the star's visible surface rather than showing separate blotches or patches of contrasting color; the star's overall brightness looks steady from start to finish, matching the idea that its total light output doesn't suddenly jump or drop; the final orange-red the star reaches is clearly distinct from its starting yellow-white, without settling on an ambiguous in-between shade.

Spatiotemporal Consistency rubric:
level_1: The star vanishes and then reappears, splits into separate pieces, becomes extremely stretched or torn-looking, or the light and shadow around it flash violently or reset partway through.
level_2: The star stays visible but has a major continuity break: for example it visibly jumps to a new position or size between one moment and the next, flips or spins suddenly, or appears to pass behind something invisible and comes back at a different size; or its motion looks like a rapid strobe.
level_3: The star stays continuously visible in roughly the same part of the frame, and its size and color change smoothly with no jump cuts, no fragmenting, and no sudden collapse of its shape; the overall scene brightness does not suddenly pulse or flash in a way that breaks the sense of continuous time passing.
level_4: Everything in score 3 holds, and in addition the star's edge stays sharp and steady rather than flickering, stepping jaggedly, or vanishing in and out; the background stays still (or shifts only in a way consistent with a fixed camera); the star's growth looks fluid, without stuttering or dropped-looking moments.
level_5: Everything in score 4 holds, and in addition the star's growth proceeds in one steady direction with no reversal or sudden speed-up; there is no glowing trail, ghost outline, or blur left behind the star's expanding edge that looks physically wrong; the star's center stays essentially in the same spot in the frame throughout, without drifting or panning off to one side.