Conciseness

Lean and dense throughout: it never explains basic concepts (canvas, Matrix4, InstancedMesh, IntersectionObserver) and instead spends its tokens on earned domain insight ('That instant of near-disappearance is what the eye reads as leaf'; 'The eye finds the common rhythm in about two seconds'), assuming Claude's competence.

Actionability

Fully executable, copy-paste-ready code blocks cover the common cases — the 2-D tumble (`ctx.scale(Math.cos(l.spin), 1)`), the slip coupling (`l.x += Math.sin(l.spin) * l.slip * dt`), the 3-D ahead-of-camera recycle disc, and the viewport-area count scaling — with concrete parameter ranges in the layer table.

Workflow Clarity

A single-purpose build skill with a clear ordered build sequence (tumble first → couple slip → bake faces → vary params → recycle → density → layer → colour → budget → pause → reduced motion) closing in an explicit 'Verify' checklist of validation checkboxes, satisfying the simple-skill exception.

Progressive Disclosure

No bundle files exist and none are needed: the body is a single self-contained file organised into well-signalled section headers, with nothing (no API reference or large lookup table) that clearly belongs in a separate one-level-deep reference.

Specificity

Names the domain and lists multiple concrete build aspects — '2-D canvas build and the instanced-3-D variant', 'leaves are recycled', 'density-versus-count maths', 'depth layering', 'colour under a tone-mapped composite', 'reduced motion, and visibility pausing' — giving comprehensive coverage rather than a single generic action.

Completeness

Explicitly answers both halves: the 'what' ('Build falling leaves that read as leaves, with each one tumbling on its own axis...') and the 'when' ('Use for autumn maple, sakura petals, blossom, ash, snowfall shapes, or any drifting foliage where a generic particle field reads as confetti').

Trigger Term Quality

Comprehensive natural-term coverage including synonyms and concrete shapes a user would actually say: 'falling leaves', 'autumn maple', 'sakura petals', 'blossom', 'ash', 'snowfall shapes', 'drifting foliage', plus the contrast term 'confetti'.

Distinctiveness Conflict Risk

A clear niche (recognisable drifting foliage) with an explicit boundary against the generic-particle-field neighbour ('where a generic particle field reads as confetti'), so it is unlikely to trigger for the wrong skill.