Conciseness

The body is lean and imperative throughout — "Clamp frame indexes to 0...frameCount - 1", "Cap device pixel ratio at 2" — with zero padding and no explanation of concepts Claude already knows. Two short code blocks earn their tokens; every line instructs. Matches the 5 anchor.

Actionability

Executable snippets for the sequence config, progress normalization, and ScrollTrigger setup, plus specific directives ("Encode frequent keyframes", "redraw only when progress changes"). Not 5 because the dependency-free implementation is only described ("measure the section on scroll and resize") rather than shown, and several media-safety bullets (e.g., "Cancel stale image requests") state the goal without the mechanism.

Workflow Clarity

The sections form a coherent build sequence (define → choose renderer → build stage → handle media → access → tune → verify), with a numbered 6-step stage build and a determinism invariant ("The same scroll position must always reproduce the same state"). The Verify section is an explicit checklist covering forward/reverse, fast flicks, resize, viewport widths, reduced motion, and cleanup, matching the 5 anchor's validation and checklist criteria. Not 4 because checkpoints are explicit rather than implicit.

Progressive Disclosure

References to [demo/index.html](demo/index.html), [demo/PROMPT.md](demo/PROMPT.md), and [REFERENCES.md](REFERENCES.md) are clearly signaled and one level deep, but none of these files exist in the bundle, so the navigation they promise is broken. Not 4 because missing referenced files are more than a minor organization gap; not 2 because the body itself is well-sectioned and self-contained in its guidance.

Specificity

The description enumerates concrete capabilities: "Build reversible scroll-controlled visual transformations with a pinned or sticky stage, normalized progress, and video, image-sequence, canvas, SVG, or DOM renderers" — multiple specific actions with comprehensive renderer coverage. Not 4 because coverage of the what is complete rather than having minor gaps.

Completeness

Explicitly answers both what ("Build reversible scroll-controlled visual transformations...") and when ("Use for hero transformations, product assembly, ... that must move forward and backward with native scrolling"). Matches the 5 anchor with concrete trigger phrases; a missing or weak 'Use when' clause would cap this at 3, which is not the case here.

Trigger Term Quality

Good natural triggers such as "hero transformations", "product assembly", "interface state walkthroughs", "object rotation", "diagrams, or photo sequences", but common user phrasings like "scroll animation", "video scrubbing on scroll", or "Apple-style scroll effect" are missing. Not 5 because synonym/colloquial coverage is incomplete; not 3 because the included terms are natural, not jargon-only.

Distinctiveness Conflict Risk

"Reversible scroll-controlled visual transformations" with "pinned or sticky stage" and "normalized progress" carves a clear niche with distinct triggers; minimal overlap risk with generic animation or layout skills. Not 4 because the trigger list (scroll-driven, reversible, scrub-style sequences) is not shared with closely related skills.