spacingskill: The Spacing & Rhythm Skill

> For any UI or written document an agent generates or edits — landing > pages, dashboards, forms, data tables, mobile screens, editorial, and > Word / Google Docs / PDF / Markdown documents (§14). > Spacing is the single fastest tell of AI-generated UI: off-scale magic > numbers, everything equally cramped, no proximity hierarchy, optical > misalignment. > Every rule below is contextual. Nothing fires automatically. First read > the layout, set the dials, then pull only what fits. Spacing is a system, > not decoration applied at the end.

0. SPACE INFERENCE — Read the Layout Before a Single Pixel

Spacing is a decision made BEFORE the first <div> exists. Infer it; do not default to it. State the dials, emit one "Space Read" line, then generate.

0.A Signals to read (priority order — higher overrides lower)

| # | Signal | Where it comes from | What it sets | |---|--------|---------------------|--------------| | 1 | Existing scale / tokens | Tailwind config, --space-* / --spacing vars, a component lib (MUI/Carbon/Radix/Chakra), repeated literals | SPACING_STEP + the whole scale. Conform, do not invent. | | 2 | Brand / explicit constraint | Brand guide, "match our app", a referenced screenshot, a stated number | Overrides aesthetic preference. Lock it, build around it. | | 3 | Surface kind | table vs hero vs form vs dashboard | DENSITY + SPACING_STEP start | | 4 | Density the CONTENT demands | field count, columns, rows/screen, words/block, scan-vs-read | Final DENSITY. Content outranks aesthetic. | | 5 | Grouping relationships | how many groups; nesting depth | the spacing ramp + ALIGNMENT_RIGOR | | 6 | Viewport range | mobile-only, responsive, desktop-app, TV | margins/gutters + how DENSITY shifts across breakpoints |

• Detect-and-conform is rule zero. If a scale exists, SPACING_STEP is already decided — adopt it. Introducing a second scale beside an existing one produces 13px/22px values that read as broken. This is the most damaging spacing error.
• Content demand outranks the surface stereotype. A "marketing page" that is really a 9-row pricing table is a data surface — raise DENSITY. Classify by what the content does (scan / compare / read / input), not its label.
• Grouping is the real job. The deliverable is almost never "more space"; it is a correct ratio — items in a group sit closer to each other than to the next group (§6).
• Viewport sets margins, not the whole system. SPACING_STEP stays constant across breakpoints; outer margin and sometimes DENSITY change. Mobile gets a smaller margin (≈16px), never zero.

0.B State the "Space Read" FIRST, every time

One line before any markup. It makes the inference explicit and reviewable, and locks the dials so the user can redirect in one sentence.

> Space Read: <surface> · <airy|balanced|packed> · STEP <n> · DENSITY <n> · RIGOR <n> · <the one ratio/constraint that matters>

| Situation | Space Read | |-----------|------------| | Admin table, 7 cols, 30 rows | data-table · packed · STEP 4 · DENSITY 8 · RIGOR 9 · row rhythm 8px, columns hard-snapped, numerals right-aligned | | SaaS landing hero + 3 cards | marketing-hero · airy · STEP 8 · DENSITY 2 · RIGOR 5 · section padding 96–128px, generous lead under headline | | Settings form, existing Tailwind | form · balanced · STEP 4 (inherited) · DENSITY 5 · RIGOR 8 · label↔input 8px, field↔field 24px, group↔group 40px |

If you cannot fill the final clause, you have not finished reading the situation — do not start coding.

0.C Anti-Default Discipline — forbidden LLM reflexes

| Forbidden default | Why it's wrong | Do instead | |-------------------|----------------|-----------| | Uniform padding everywhere | destroys grouping; reads as one flat list | apply the §6 proximity ladder — inner gap < outer gap | | Magic numbers (13, 17, 22px) | on no grid; reads as broken | every value = a multiple of SPACING_STEP | | Mixing two scales | cumulative drift, nothing lines up | one SPACING_STEP for the whole tree | | Airy by default on dense data | wastes the screen the content needs | DENSITY follows content (0.A.4) | | gap: 10px / 20px / 30px | base-10 ≠ the grid | snap to 8/12/16/24 | | Equal margin above & below a heading | heading belongs to the content below | ~2:1 above:below (§5) | | Zero outer margin on mobile | cramped, unreadable | ≥16px screen margin for text | | Centering everything | no alignment spine; weak scanning | left-align body; center only hero/empty states | | Sub-target tap areas | fails a11y | ≥24×24px (WCAG AA); 44pt/48dp on touch | | Cramming to fit "above the fold" | breaks rhythm for a myth | hold the ramp; let content scroll |

1. THE THREE DIALS — Core Configuration

Set three dials after the Space Read. Every later decision is gated by them.

• SPACING_STEP — base grid unit (px). 4 = fine/dense data UI, 8 = default clean layout. Avoid odd bases. Every spacing value is a multiple of it (the 0.5× half-step is the only sub-unit, for hairline/icon↔label gaps).
• DENSITY — 1 = art-gallery airy (marketing, hero) … 10 = cockpit packed (tables, terminals). It does not invent numbers; it selects which rungs of the scale you reach for.
• ALIGNMENT_RIGOR — 1 = freeform/editorial … 10 = strict column- & baseline-grid-locked. Governs how hard elements snap to columns, edges, and a shared text baseline. Governs snapping, not gap size — an airy layout can still be strictly aligned.

Baseline (no signal): 8 / 4 / 7. Overrides happen conversationally, never by asking the user to edit this file (see §13.B).

1.A Dial inference (signal → dials)

| Signal in the Space Read | STEP | DENSITY | RIGOR | |--------------------------|:---:|:---:|:---:| | Marketing / hero / landing | 8 | 1–3 | 4–6 | | Editorial / brand piece | 8 | 2–4 | 1–3 | | Standard app UI / forms / settings | 8 | 4–6 | 7–8 | | Dashboard (mixed cards + tables) | 8 (4 inside tables) | 6–8 | 8 | | Data table / terminal / cockpit | 4 | 8–10 | 9–10 | | Docs / long-form reading | 8 | 3–4 | 5–6 | | Mobile primary | 8 | 4–6 | 7 |

Inference rules:

• Compute DENSITY: start at the midpoint of the §1.A range, apply the §1.B deltas (they sum), then clamp to 1, 10]. When a §1.B content shift contradicts the §1.A surface band, content wins (§0.A) — let the value leave the band (a marketing-hero surface holding a 9-row pricing table lands dense, not airy).
• SPACING_STEP = 4 only when DENSITY ≥ 7 (and as a 4-grid local override inside a dense region of an 8-grid page). The 4-scale is a strict subset of the 8-scale, so one product stays coherent.
• DENSITY and gap move inversely: high DENSITY pulls every gap one rung down; low DENSITY pushes section gaps one rung up.
• ALIGNMENT_RIGOR rises with repetition — many repeated rows/cells → 8–10; few bespoke blocks → 1–4. The 7 baseline applies only absent any repetition/bespoke signal; a present "few bespoke blocks" signal overrides it to 1–4. High DENSITY does not mean low RIGOR; packed UIs need more rigor.

1.B Content adjustments to DENSITY

| Observed | Shift DENSITY | |----------|:---:| | > 6 columns OR > 20 rows visible | +2 | | Numeric / financial / monitoring data | +1 | | > 8 input fields in one view | +1 | | Primary action is compare / scan | +1 | | Primary action is read (prose) | −2 | | Single focal CTA, little else | −2 | | "spacious / premium / calm" | −1 to −2 | | "compact / power-user / efficient" | +1 to +2 |

Deltas sum, then clamp DENSITY to [1, 10]. On a content-vs-aesthetic conflict the content delta wins (§0.A) — "numeric/financial +1" beats "premium −1".

2. THE SPACING SCALE — One Scale, No Magic Numbers

Every spacing value resolves to a rung on one scale derived from SPACING_STEP. If a number is not on the scale it is a bug — except the one hairline exception in §2.D. 8 is the default because Material, Apple HIG, IBM Carbon, and Tailwind's effective layout steps all converge on an 8px rhythm; 8 divides cleanly at common zoom/DPR factors and keeps steps visually distinct.

2.A The canonical scale (SPACING_STEP = 8)

Keyed by px (the universal truth) with rem and the matching Tailwind utility. px = SPACING_STEP × multiplier. Spacing is linear (multiples of the step) so it tiles and nests on a grid — never a modular/fractional scale for layout (modular is for type, §5, and the macro exception in §2.C).

| px | mult | rem | Tailwind | Typical use | |---:|:---:|:---:|:---:|-------------| | 0 | 0 | 0 | p-0 | reset / collapse | | 4 | 0.5× | 0.25 | p-1 | hairline gap, icon↔label, tightest pair | | 8 | 1× | 0.5 | p-2 | tight inline gap, compact vertical inset | | 12 | 1.5× | 0.75 | p-3 | compact control padding | | 16 | 2× | 1 | p-4 | default gap between related items, control pad-x | | 24 | 3× | 1.5 | p-6 | card inset, field↔field, related-group gap | | 32 | 4× | 2 | p-8 | group separation, large card inset | | 48 | 6× | 3 | p-12 | sub-section gap | | 64 | 8× | 4 | p-16 | section gap (compact) | | 96 | 12× | 6 | p-24 | major section gap (marketing) | | 128 | 16× | 8 | p-32 | hero vertical rhythm | | 160 | 20× | 10 | p-40 | airy landing rhythm (DENSITY ≤ 3) |

For SPACING_STEP = 4: halve every px — the in-between rungs (4 / 8 / 12 / 16 / 24 / 32 …) become load-bearing. Nothing is dropped; the dense scale is the 8-scale with finer resolution.

> Tailwind note: Tailwind's unit is 4px (p-4 = 16px). The Tailwind column above is matched by px, not by index — always pick the utility whose px equals your target (16px → p-4), and never p-[13px].

2.B Primitive vs semantic tokens

Two tiers. Primitives are the raw scale. Semantic aliases name a job and point at a primitive, so a density change edits one mapping, not 200 call-sites. Components consume semantic tokens; only the theme layer touches primitives.

| Semantic | Job | DENSITY 1–3 | DENSITY 4–7 | DENSITY 8–10 | |----------|-----|:---:|:---:|:---:| | inset-md | standard card/panel padding | 48 | 24–32 | 16 | | gutter | column / grid-cell gap | 64 | 32–40 | 16 | | section | gap between page sections | 128–160 | 96 | 48 | | stack-sm | vertical gap between stacked items | 24 | 16 | 8 |

2.C Modular scale — only for the macro tier

For section rhythm on low-DENSITY marketing pages, a geometric scale (stepₙ = base × ratioⁿ) gives more deliberate jumps — then snap each result to the nearest grid multiple. Allowed only when ALIGNMENT_RIGOR ≤ 4 and DENSITY ≤ 4 and the spacing is between full page sections. At RIGOR ≥ 7 stay linear (a baseline-locked grid can't absorb the snap residue).

Pick the ratio by DENSITY: 1.25 at DENSITY 4 (restrained) · 1.333 at 3 (editorial) · 1.5 at 2 (dramatic) · 1.618 at 1 (hero only). Example (base 16, ×1.5, snapped to 8): 16 → 24 → 40 → 56 → 80. The unsnapped 36/54/81 are forbidden.

2.D The ONE allowed off-scale exception

Hairlines, borders, and rendered lines live off the spacing scale. A 1px border, 0.5px retina rule, outline-offset, and optical-centering transform nudges (≤4px — typically 1–2px, up to 4px only for large display glyphs) are rendered lines, not layout space. The gap around a border is still on-scale. Nothing else escapes.

2.E Emitting tokens

css
:root {
  --space-step: 8px;
  --space-1: calc(var(--space-step) * 1);   /* 8  */
  --space-2: calc(var(--space-step) * 2);   /* 16 */
  --space-3: calc(var(--space-step) * 3);   /* 24 */
  --space-4: calc(var(--space-step) * 4);   /* 32 */
  --space-8: calc(var(--space-step) * 8);   /* 64 */
  /* semantic aliases point at primitives — density edits these only */
  --inset-md: var(--space-3);
  --gutter:   var(--space-4);
  --section:  var(--space-12, 96px);
}

3. SPACING PRIMITIVES & GAP OWNERSHIP

Every gap expresses a relationship. Name the relationship → the primitive is determined.

| Primitive | Spaces | Mechanism | Use when | |-----------|--------|-----------|----------| | Stack | siblings stacked vertically | parent flex-direction:column; gap | form fields, list rows, sections | | Inline (cluster) | siblings in a row | parent flex; gap (+ align-items) | button rows, tag clusters, toolbars | | Inset | a container & its own children | padding on the container | inside card/button/input/section | | Grid-gap | cells of a 2-D grid | display:grid; gap | card galleries, dashboards, matrices |

One axis of siblings → Stack/Inline. Container-to-content → Inset. Two-axis repetition → Grid. Inset is the only primitive that uses padding; Stack/Inline/Grid express between with gap. On a wrapping flex/grid container, one gap owns both the inline gap and the cross-axis gap between wrapped rows (align-content distributes leftover cross space) — chip/tag clusters wrap with even spacing from one declaration.

3.A The single-owner law — one gap, one owner

The space between two elements has exactly one owner. Never let A's margin-bottom and B's margin-top both contribute — you get an unpredictable sum (or a surprise collapse).

• Default everywhere: gap on the flex/grid parent. Single-owner by construction; children declare zero margins. This is the highest-leverage rule in the skill.
• Margins are a one-direction fallback for free-flowing prose where children aren't a known set — pick margin-block-end-only and never deviate.
• Inset never doubles with gap. A card's padding owns edge-to-content; the grid's gap owns card-to-card. They meet but never sum.

css
.stack { display: flex; flex-direction: column; gap: var(--space-2); }
.stack > * { margin: 0; }

If you ever compute a gap as "8 here plus 8 there = 16", you have two owners. Collapse to one.

3.B DENSITY selects which rungs

| DENSITY | Section gap | Card inset | Stack gap (related) | Inline gap | |---------|:---:|:---:|:---:|:---:| | 1–3 (airy) | 64–96 | 32–48 | 16–24 | 12–16 | | 4–6 (default) | 32–48 | 16–24 | 12–16 | 8–12 | | 7–10 (data/cockpit) | 16–24 | 8–12 | 4–8 | 4–8 |

At DENSITY ≥ 8 set SPACING_STEP = 4 so tight gaps still land on grid.

4. LAYOUT GRID & ALIGNMENT

4.A Column grid, gutters, page margins

Use a 12-column grid (divisible by 2/3/4/6) when content must align across rows of differing components. Gutters and page margins are fixed per breakpoint; column widths are fluid (%/fr). Material 3 reference: 16dp margins at compact, 24dp gutters + margins at the tablet range.

| Viewport | Columns | Gutter | Page margin | |----------|:---:|:---:|:---:| | Mobile (<600) | 4 | 16 | 16 | | Tablet (600–1024) | 8 | 24 | 24 | | Desktop (>1024) | 12 | 24–32 | clamp, see 4.B |

css
.grid-12 { display: grid; grid-template-columns: repeat(12, 1fr); gap: var(--gutter); }

Use minmax(0, 1fr) for fluid tracks so a long unbroken string can't blow out a column and break the gap; reach for fit-content/min-content where a track should hug its content. This also protects the §9.D reflow guarantee.

4.B Measure & content max-width

Unbounded text on wide viewports destroys readability. Cap the measure at 45–75 characters (~66 ideal). Use ch for prose so the measure holds across font sizes; center the block with margin-inline:auto, keep page margins as padding-inline so text never kisses the edge.

css
.prose { width: min(100% - 2 * var(--page-margin), 65ch); margin-inline: auto; }

4.C Alignment toolkit (reach for these before any margin/auto hack)

| Property | Axis | Use | |----------|------|-----| | justify-content | main / inline | distribute along the row (space-between for logo↔nav, space-evenly for segmented controls) | | align-items | cross | line items up across the cross axis (baseline for icon+text, number+label) | | align-content | wrapped lines | distribute wrapped rows | | place-items | both (grid) | place-items:center centers a single child on both axes | | gap | both | the space owner (§3.A) |

• Mixed-height inline items must align to text → align-items:baseline, not center.
• Equal-height cards in a row → align-items:stretch + a flex-column card with margin-top:auto on the footer (the one sanctioned auto-margin — it pushes within a flex child, owns nothing between siblings).
• ALIGNMENT_RIGOR: at 1–3 freeform centering and optical nudges are fine; at 7–10 every edge lands on a column line and body content uses start/stretch (not center) so left edges lock to the grid.

4.D Subgrid — align nested card content across siblings

Cards with different title lengths lose internal alignment. align-items:stretch equalizes height but not internal tracks. Subgrid fixes it — each card adopts the row's tracks, so titles/bodies/footers align across the row regardless of text length (widely supported: Chrome/Edge 117+, Firefox 71+, Safari 16+).

css
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-6); }
.cards > .card { display: grid; grid-row: span 3; grid-template-rows: subgrid; }

4.E Centering — by what you're centering

| Situation | Strategy | |-----------|----------| | One element, both axes | display:grid; place-items:center | | One element horizontally, block flow | margin-inline:auto + max-width | | Text within its box | text-align:center (text only) | | A row of items as a group | flex parent + justify-content:center |

Never center long-form body copy (ragged edges wreck the return sweep) — center the block, left-align the text. Centering is a DENSITY 1–4 move; at higher density / RIGOR ≥ 6, left-align and lock to the grid.

5. VERTICAL RHYTHM — Type Drives Spacing

Vertical space is emitted by the text. Line-height is the atom; set type first, then let it dictate rhythm.

5.A Line-height is the base unit

The line box (computed line-height), not the font size, is what stacks: 16px × 1.5 = a 24px line box. Reason in line boxes.

| Role | line-height | Why | |------|:---:|-----| | Body / paragraph | 1.5–1.6 | WCAG 1.4.12 needs ≥1.5; ship 1.5 minimum | | Long-form reading | 1.6–1.75 | longer measure needs taller leading | | UI body / dense rows | 1.4–1.5 | tighter, never below 1.4 on wrapping text | | Headings (large type) | 1.0–1.25 | big glyphs need less leading | | Single-line labels/buttons | 1.0–1.2 | inset owns the height (5.E) |

Leading shrinks as size grows. DENSITY trims leading before gaps (≥7 → 1.4; ≤3 → 1.6+), but never below 1.4 on wrapping text regardless of DENSITY.

Stacked-diacritic scripts raise the heading floor. Scripts whose marks stack both above and below a letter — Vietnamese (Ệ Ợ Ằ Ầ), and similarly Thai / Arabic / Devanagari — need multi-line headings held at line-height ≥ 1.1: below ~1.05 an under-dot on one line collides with a circumflex/breve on the next. Latin all-caps tolerates 0.95; the same heading set in Vietnamese does not. This is gated by the content language, not by taste — a leading-[0.95] display heading is a latent collision the instant it wraps to two lines of marked caps, so set the floor whenever the text can be localized into a mark-stacking script.

5.B Baseline grid — pragmatic, not dogmatic

Round the computed line-height to a multiple of SPACING_STEP so every line lands on the grid (16px body → 24px line box on an 8-grid). Align line boxes to the grid; don't chase per-font baselines. ALIGNMENT_RIGOR: ≤3 loose multipliers, no snapping; 4–7 snap line-heights and block gaps (headings may break locally); ≥8 snap everything and insert a corrective spacer to re-sync after off-grid media (images, embeds).

5.C Heading spacing is ASYMMETRIC — more above, less below

A heading belongs to the content beneath it. Space above separates it from the previous block; space below must be smaller so it bonds to its paragraph. Equal space orphans the heading. Ratio above ≈ 2–3× below; both are scale multiples. Zero out the top space on a :first-child heading (the container's padding owns it).

| Level | font-size | above | below | |-------|:---:|:---:|:---:| | H1 / page title | 36–48 | 48 | 16 | | H2 / section | 28–32 | 40 | 16 | | H3 / subsection | 22–24 | 32 | 12 | | H4 | 18–20 | 24 | 8 | | H5 / eyebrow | 14–16 | 16 | 8 |

Collapse the asymmetry into one owner (heading margin-top + small/zero margin-bottom, or container gap) — never set both heading margins and the next paragraph's top margin.

5.D A paired modular TYPE scale

Type scale and spacing scale share the same SPACING_STEP rhythm so sizes and gaps never fight. Ratio by context: 1.333–1.5 for marketing (DENSITY ≤3), 1.25 (major third) default, 1.2–1.125 for dense UI (≥7). Material 3's line-boxes are 4-grid-aligned (body 16/24, title 22/28, headline 24/32, 28/36, 32/40, display 57/64) — note some font-sizes (e.g. 57) aren't multiples of 4, so anchor the rhythm to the line boxes, not the sizes.

5.E Control heights = line-height + inset, never a clamped fixed height

A button/input height is line-height + padding + borders — computed, not asserted. A rigid height:36px with centered text clips descenders (g, y, p) when font/zoom/line-height change. Use min-height (a floor), never height (a clamp).

| Control | font / lh | inset (each side) | height | grid | |---------|:---:|:---:|:---:|:---:| | Small | 14 / 20 | 6 | 32 | 4× | | Medium | 14–16 / 20–24 | 8–10 | 40 | 5× | | Large | 16 / 24 | 12 | 48 | 6× |

Vertical inset is a derived value — pick it so total height lands on a grid multiple (the grid-locked quantity is the height 32/40/48, so a computed inset like 6px is exempt, like line-height). Inset is the density dial (≥7 → tighter, ≤3 → 12–14px), but the touch target must still clear 44×44px / 48×48dp — pad the hit area, never shrink the target (§9).

6. WHITESPACE HIERARCHY — Proximity = Relationship

Whitespace is not leftover; it is the primary grouping signal. The eye groups by distance pre-attentively (~100–150ms), before reading a word. Spacing decides structure whether you control it or not.

6.A The Law of Proximity

Closer reads as related; farther reads as separate — distance overrides border, color, and similarity. The signal is the ratio between gaps, not any absolute value. A 12px gap means "tighter than the 24px gap beside it." Ambiguous spacing (tiers too close in size) reads as flat noise — fix by widening the larger tier, not shrinking the smaller.

6.B The Proximity Ladder — the core mental model

Every gap belongs to exactly one tier. Assign the tier, then pull px from the scale.

| Tier | Separates | Reads as | |------|-----------|----------| | Intra-item | parts of ONE atom (label↔input, icon↔text, number↔unit) | one indivisible unit | | Inter-item | sibling atoms in a group (two fields, two rows) | distinct but related | | Inter-group | whole groups / sections | separate concerns |

Non-negotiable rule: each tier must be clearly larger than the one below — target ≥2×, never < ~1.5×. Below 1.5× the eye can't separate the tiers. Clean ladders: 8 → 16 → 32 (each 2×) at STEP 8, 4 → 8 → 16 at STEP 4. Three tiers is usually enough; add a fourth (→ 64) only for full pages.

6.C A label + its control is ONE unit

The label → input gap is intra-item — the tightest tier. Always keep label→input < input→nextField (e.g. 8 < 16). Violating this single inequality is the most common form-spacing bug; it makes the label detach and the form fragment.

6.D Macro vs micro whitespace

Micro (inside/between atoms: line-height, padding, intra/inter-item gaps, steps 4–16) drives legibility — get it right for usability. Macro (between sections/regions, steps 32–96+) drives feel — thin macro whitespace reads as cheap. They are set independently: a dense table can have tight micro spacing and generous macro margins.

6.E Active whitespace = emphasis

Isolation is emphasis. When something matters more, give it more surrounding space — a primary CTA with 2× the breathing room of its neighbors reads as primary without extra weight or color.

6.F Reach for whitespace BEFORE borders and boxes

Separation ladder — stop at the lightest tool that resolves the grouping: whitespace → background tint → hairline divider (1px) → border → filled card. A card is justified only when the surface scrolls independently, is draggable/selectable, or genuinely floats (elevation). If a card contains only spacing and no independent behavior, delete the card and keep the spacing. Never double-encode (a gap and a divider for the same break).

7. OPTICAL ALIGNMENT — Trust the Eye

The eye, not the math, is the acceptance test. Metric centering is correct only for symmetric shapes; everything asymmetric needs a nudge toward visual mass. ALIGNMENT_RIGOR gates how many fixes fire — never whether the egregious ones do.

7.A Rigor gate (apply top-down until the budget runs out)

| RIGOR | Fires | Skips | |:---:|-------|-------| | 1–3 | lone glyph in a circular button; icon↔text vertical centering | hanging punctuation, overshoot, mass correction | | 4–6 | + asymmetric icon nudge (play/chevron/arrow); button icon asymmetric inset; bullet/marker hang | per-icon optical sizing, sub-pixel quote hang | | 7–10 | + hanging punctuation & quotes, overshoot tuning, equal-gap mass correction | nothing — full optical pass |

An asymmetric mark metric-centered is a bug at any rigor — fix it even on an art-gallery page. DENSITY scales nudge magnitude: ~1px at DENSITY ≥7 (small glyphs; over-correction reads as error), 2–4px at ≤3 (large display glyphs).

7.B Asymmetric glyph nudges (≈24px icon; scale ≈ round(size/16)px, clamp 1–3)

| Mark | Direction | Nudge @24px | |------|-----------|:---:| | Play ▶ in a circle | right, toward the apex | +1 to +2px translateX | | Chevron › / ‹ | toward the point | +1px | | Caret ▾ (dropdown) | down | +1px translateY |

Do this in the artwork or a wrapper transform — never by unbalancing the button's padding (that breaks the touch target).

7.C Icon ↔ text — the most common real bug

Size an inline icon to ≈cap-height and sit it on the cap band, not the line box (a 1em icon floats above the optical center):

css
.inline-icon { width: 1em; height: 1em; vertical-align: -0.125em; }

Prefer the cap unit where supported; otherwise -0.1em to -0.15em is the safe default. In dense rows, baseline-lock the icon to the row's text baseline.

7.D Hanging punctuation, quotes, list markers (RIGOR ≥ 6)

Pull marks into the margin so the text edge — not the punctuation — aligns to the column. Opening quotes hang ≈0.4–0.5em; bullets use list-style-position: outside; numbered lists right-align numerals (tabular figures); use hanging-punctuation: first where supported. Failure mode: a blockquote whose visible text starts a quote-width right of the body column.

7.E Button optical padding — icon beside a label

Inset asymmetrically: tighter on the icon side, looser on the label side (a metric-equal pad crams the icon). At STEP 8 / DENSITY 4–6: padding: 8px 16px 8px 12px for a leading-icon button; mirror for trailing. Icon↔label gap = one step, and always tighter than the outer pad so the pair groups. Icon-only buttons return to symmetric padding.

7.F Overshoot & equal-gap-unequal-mass (RIGOR ≥ 7)

Round/pointed shapes must slightly exceed cap height to look equal (≈1–3% for a circle/dot vs an adjacent square; below 16px, snap to whole pixels). For cards of unequal content with equal gaps: equalize visual mass — pad the sparse card more so ink-to-space ratio matches its neighbor, adjusting by whole SPACING_STEP units. Squint test: misaligned mass survives blur; metric-but-balanced alignment dissolves into even gray.

8. RESPONSIVE & FLUID SPACING

Space is a function of viewport and container — resolve it with math, gate the breakpoints with the dials, and let components respond to their width.

8.A clamp() for fluid section rhythm

clamp(MIN, PREFERRED, MAX) replaces a breakpoint stack. PREFERRED carries a vw term so it scales; always include a rem term so it survives zoom, and snap MIN/MAX to the scale (mid-scroll interpolation off-grid is invisible).

css
/* 48px @360 → 128px @1440, STEP 8 */
.section { padding-block: clamp(3rem, 1.33rem + 7.41vw, 8rem); }

| Signal | clamp band | |--------|-----------| | Hero / section, DENSITY 1–3 | clamp(4rem, …, 10rem) | | Standard section, DENSITY 4–6 | clamp(3rem, …, 6rem) | | Dense app shell, DENSITY 7–10 | clamp(1rem, …, 2rem) | | Component padding | clamp(1rem, …, 1.5rem) — narrow band |

Keep the fluid band wide for large spaces, narrow for small ones — a 4px→40px icon gap reads as broken.

8.B Step DENSITY +1 on mobile — outer skeleton only

On narrow viewports, compress layout gaps (section/margin/gutter drop 1–2 steps) but hold intra-item gaps and touch targets. If a gap separates layout regions, it is compressible; if it separates parts of one comprehensible unit, it is not.

The same test governs COLUMN COUNT — and a blanket "collapse everything to one column" is where a phone screen gets spent. Reflow (§9.D) requires no horizontal scroll; it does not require a single column. Set the mobile column count from the narrowest cell's content demand, not from the grid it happens to live in: a cell holding one number and its label wants about half a phone's width, while a cell holding a table, a chart or prose wants all of it. A four-up stat row therefore belongs two-up at 375px — collapsing it costs roughly a screen of scroll per four cells (measured on one dashboard: 822px of stat cards before the first real content, 371px after the same four went two-up). Target the row that holds the small cells (:has(> .stat), or a modifier class where :has() is not available) rather than the breakpoint as a whole, so cells that genuinely need the width still get it.

8.C Container queries vs viewport

A component should respond to its container, not the window — a card in a 320px sidebar and a 900px column differ at one viewport width. Page chrome → @media; everything reusable inside it → @container (query inline-size for RTL safety).

css
.card-wrap { container-type: inline-size; }
@container (min-width: 28rem) { .card { --pad: 1.5rem; } }

8.D Logical properties

Author with padding-block / padding-inline / margin-inline / inset-*, not physical top/right/bottom/left. They flow with writing direction (LTR/RTL/vertical) with zero overrides and cut declarations roughly in half. In vertical writing modes (CJK), the block/inline axes swap — the §5 line-box rhythm then runs along the inline axis, so re-check the baseline logic there.

8.E safe-area insets

Pad against env(safe-area-inset-*) for edge-anchored UI (fixed headers, bottom tab bars, FABs). Requires <meta name="viewport" content="…, viewport-fit=cover"> or insets resolve to 0. Add to your token, never replace it: padding-block-end: calc(1rem + env(safe-area-inset-bottom, 0px)).

8.F vw pitfalls

Never size spacing/type with bare vw (no floor/ceiling, ignores zoom) — always wrap in clamp() with a rem term. Avoid 100vw (scrollbar overflow → use 100%/100dvw); prefer dvh/svh/lvh over vh so mobile URL-bar changes don't jump the layout.

8.G Anchored scroll under a sticky header

A fixed/sticky header (the nav in §10) hides in-page scroll targets. Reserve the space in scale multiples: scroll-padding-block-start on the scroll container = header height + a buffer, and scroll-margin-block-start on anchor targets.

css
html      { scroll-padding-block-start: calc(var(--header-h) + var(--space-2)); }
:target   { scroll-margin-block-start: var(--space-2); }

8.H Motion preserves the scale

Animate opacity/transform, never layout (gap/padding/width) — animated layout reflows the grid and breaks rhythm. Stagger list reveals by time, not by spacing. Honor prefers-reduced-motion.

9. ACCESSIBILITY — Spacing Floors That Override Every Dial

These are floors verified against the spec, not preferences. When a dial collides with a floor, the floor wins and you clamp the dial.

9.A Target size

| Standard | Minimum hit area | Level | |----------|:---:|:---:| | WCAG 2.5.8 Target Size (Minimum) | 24×24 CSS px | AA | | WCAG 2.5.5 Target Size (Enhanced) | 44×44 CSS px | AAA | | Apple HIG | 44×44 pt | platform | | Material 3 / Android | 48×48 dp | platform |

Separate hit area from visual size — a 16px icon + padding reaches the target: +4px → 24px (AA), +14px → 44px (AAA). DENSITY picks which floor (1–3 → 44; 4–7 → 24 AA, 44 on primary CTAs; 8–10 → 24 AA + the spacing exception) but never pushes a hit area below 24px.

Grow the hit box at zero layout cost — padding + negative margin. In a tight cluster on a fixed gap (header icon buttons, a VN/EN toggle, a toolbar), padding alone to reach the floor spreads the row and breaks its rhythm. Pair the padding with an equal negative margin: the padding enlarges the hit box, the negative margin restores the margin-box, so every sibling gap and edge holds. -m-2.5 p-2.5 makes a 20px icon a 40px target with the layout unmoved (-my-*/py-* for a vertical-only grow on an inline text toggle) — the actionable form of §5.E's pad the hit area, never shrink the target when the surrounding spacing is load-bearing. Re-anchor overlays to the glyph: a badge/dot set absolute on the button jumps to the padded corner once you inset it — wrap the icon (+ overlay) in an inner relative span so it stays pinned to the icon, not the hit area.

9.B The 2.5.8 spacing exception — how dense UIs stay legal

A target smaller than 24×24 passes AA if a 24px-diameter circle centered on it does not intersect another target's circle — i.e. centers ≥24px apart, so min edge-gap = 24 − targetSize.

| Undersized target | Min edge-gap | On STEP | |---|:---:|---| | 20×20 | 4px | one 4-grid step | | 16×16 | 8px | one 8-grid step |

This is the only legal way to pack interactive elements tighter than 24px — why DENSITY 8–10 tables on STEP 4 work (a 20px icon-button + 4px gutter passes AA geometrically). Also exempt: inline targets in text, user-agent-styled native controls, essential presentations.

9.C Text spacing must survive overrides — WCAG 1.4.12

Layout must not break (no clip, overlap, or lost content) when the user applies all four: line-height ≥1.5×, paragraph spacing ≥2× font-size, letter-spacing ≥0.12em, word-spacing ≥0.16em. → Never set fixed-px line-height or fixed-height text containers; default to min-height + height:auto; express vertical text spacing in rem/em/grid multiples so it scales with the override. Any overflow:hidden / white-space:nowrap text box is a failure risk. When truncation is intentional, reserve a fixed number of line-boxes with -webkit-line-clamp + min-height (never height) so rows keep their rhythm without clipping.

9.D Reflow at 320px — WCAG 1.4.10

Content must work with no 2-D scrolling at 320 CSS px wide (= 1280px @400% zoom). No fixed-px widths on layout containers (use %/max-width/minmax()); multi-column grids collapse to one column. Exempt content (tables, images, maps, diagrams, video, toolbars) may scroll in 2D — wrap it in an overflow:auto container so the page never scrolls horizontally. RIGOR's strict columns still apply within a breakpoint but never exempt the collapse below it.

No-wrap overflow (the silent one): text pinned to one line (white-space:nowrap — e.g. a stat/KPI value) overflows the instant its column is narrower than the text. The classic trigger is a multi-column metric grid inside a narrow card — sm:grid-cols-3 stats living in a lg:grid-cols-2 half-width card give ~100px columns at desktop while the value font is still ~30px. Apply both fixes: (1) size the value to fit — cap the font, or make it fluid (clamp() / a container-query cqi font); (2) drop columns when the container is narrow (@container, or a lg: step matching the card going multi-column), so a column is never narrower than the longest value. Verify by measuring scrollWidth vs the column at the narrowest breakpoint, not the widest — the bug hides on wide viewports and bites at the breakpoint where cards halve but the font/columns don't.

Scroll-region overflow (overflow-x-auto is not self-contained): an intentional horizontal scroller (pill nav, toolbar, chip row, wide table) still blows the page out when its wrapper sits in an auto-sized grid/flex track — the track grows to the scroller's max-content (every shrink-0 child laid end to end) so overflow-x-auto never engages. The classic trigger: a grid given only a desktop template (lg:grid-cols-[…]) falls back to an implicit auto column on mobile, which the scroll row inflates to thousands of px. Fix by capping the track and letting the item shrink: an explicit mobile grid-cols-1 (Tailwind = minmax(0, 1fr) — min 0, not the default auto) or minmax(0, …) tracks (§4.A), plus min-w-0 on the grid/flex item holding the scroller. Then the scroll happens inside the box. Same verify: page scrollWidth at the narrowest width, not the widest.

9.E Focus indicator — budget space for it

The ring is a spacing consumer. outline-offset ≥ 2px; reserve a gutter (width + offset, ≈4px) so the ring isn't clipped by an overflow:hidden ancestor or a neighbor. Never outline:none without an equivalent (fails 2.4.7 / 2.4.11). At high DENSITY on STEP 4, bump the focusable gutter to 8px so the ring fits.

9.F Spacing as cognitive-load reduction

Whitespace groups related controls and isolates unrelated ones — directly helping low-vision, cognitive, and attention-affected users. Enforce within-group ≤ ½ between-group at every DENSITY; even a cockpit keeps within=4 / between=8, never both equal.

9.G Forced colors & dark mode

Under forced-colors / Windows High Contrast, background tints and elevation are stripped — so the §6.F separation ladder must not rely on tint or shadow alone; keep a structural fallback (a real gap or border) so groups stay separated. In dark mode, light-on-dark elements bloom and read slightly tighter — a marginally larger gap restores equal perceived separation.

10. COMPONENT SPACING RECIPES

Stated at DENSITY 4 / SPACING_STEP 8 (baseline 8/4/7). Every value is a step multiple. As DENSITY rises, compress in this order: block inset → inline inset → sibling gap → icon/label gap → touch target (never). Nav and modals lag the curve; tables lead it.

10.A Density reference (read first; every recipe references it)

| Gap role | D1–2 | D4 | D6–7 | D8–10 | Floor | |----------|:---:|:---:|:---:|:---:|:---:| | Inner inset (block) | 24–32 | 16 | 12 | 8→4 | 4 | | Inner inset (inline) | 24–40 | 24 | 16 | 12→8 | 8 | | Icon ↔ label | 12 | 8 | 8 | 4 | 4 | | Label ↔ control | 8 | 8 | 6 | 4 | 4 | | Sibling controls in a row | 16–24 | 12 | 8 | 4 | 4 | | Stacked fields / list rows | 24–32 | 16 | 12 | 8→4 | 4 | | Card ↔ card (gutter) | 32–48 | 24 | 16 | 8 | 8 | | Section padding-block | 96–160 | 64 | 40 | 24 | 24 | | Tap target (mobile) | 48 | 48 | 44 | 44 | 44 hard |

Compression curve when no row covers a case: gap(D) ≈ baseline × 0.85^(D−4), snapped to the scale, clamped to the floor.

10.B Recipes

• Button: inline inset 16 (sm 12 / lg 24) ≈ 2× block inset 8–10; icon↔label 8; button↔button 12. Inline pad always > block pad (equal looks like a chip); icon-only is square. Size by inset, never height.
• Input / field: inline inset 12–16 (match sibling buttons so they align on a row); block inset 8–12 (height ≥40 desktop / 44 touch); label↔field 8; field↔field 16; helper/error↔field 4 (tight by intent — binds the message to its field). Keep label↔field < field↔field.
• Form: group related fields with 24 between groups, 16 within; section heading↔first field 16; submit↔last field 24 (detach the commit).
• Card: inset 16 (media-light) / 24 (content); title↔body 8; body↔action row 16; card↔card gutter ≥ card inset so the channel reads wider than the card's own breathing room (or cards merge into a sheet).
• Nav bar: treat as fixed D2–3 regardless of body density (a cramped nav reads as broken). Item↔item 24–32; logo↔first item 32–40; height 56–64; tap targets inside still ≥44.
• Modal / dialog: inset 24 (mobile 16) — larger than a card; header↔body 16; body↔footer 24; footer button↔button 12; close (×) at the inset corner with a 44px hit area. Compresses last of all surfaces.
• Table / list row: the canonical high-DENSITY component — design at D8–10 even in a D4 app. Row block inset 12→8→4 (the primary density lever); inline inset 16→12→8; cell inset is the column gap; group header 16 above / 8 below (asymmetric). Below 4px block inset, switch to fixed row-height + divider rules.
• Chips / tags: inline inset 8–12, block 4–6; icon↔label 4–6; chip↔chip 8 (row+column equal). Already dense — ignore much of the curve, but a removable chip's × still needs a 44px touch hit.
• Dropdown / menu: item block inset 8–10 (height ≥36 / 44 touch), inline 12–16; icon↔label 8; label↔trailing shortcut auto (min 24 gap); list inset 4–8 so first/last item isn't flush.
• Section (landing): marketing inverts the default — live at D1–2. padding-block: clamp(6rem, 4rem + 8vw, 10rem) (96→160); heading↔content 24–32; content↔CTA 32–48; padding-inline: clamp(1rem, 0.5rem + 4vw, 4rem) (16→64). Section-to-section space is the biggest "premium vs cheap" signal.
• Avatar / media: avatar↔text 8–12; avatar-stack overlap −8 to −12; media↔caption 8; lock media with aspect-ratio + object-fit:cover, not fixed height.
• Chart / data-viz: apply the §6 proximity ladder to data — inter-bar gap < inter-category gap (e.g. bars 4–8, categories 16–24); plot inset for axis labels 24–32; legend↔plot 16; gridline/tick density tracks DENSITY (sparse at ≤3, dense at ≥7). Negative space inside the plot is breathing room — don't fill it.

11. COMMON SLOP — Anti-Patterns (Fix on Sight)

Spottable in a screenshot or diff in under three seconds. The meta-rule: spacing must encode relationship. Slop applies one number everywhere because it has no model of what belongs to what.

| # | The tell | Why it's slop | The fix | |---|----------|---------------|---------| | 1 | Uniform padding everywhere | no proximity hierarchy | differential ladder: intra 1 step, inter-group 2–3 steps (§6) | | 2 | Off-scale magic numbers (13/17/23px) | untraceable to any grid | snap to nearest step: 13→12/16, 17→16, 23→24 | | 3 | Orphaned heading (symmetric margins) | reads as unowned | above ≥ 2× below (§5.C) | | 4 | Sub-minimum touch targets | fails WCAG 2.5.8 | ≥24×24; 44/48 on touch (§9) | | 5 | Double-owned gap (child margin + parent gap) | brittle summed spacing | one owner; prefer parent gap (§3.A) | | 6 | Fixed desktop spacing on mobile | crushes content; h-scroll | fluid inset clamp(16px, 5vw, 64px) | | 7 | Over-boxing (a card per group) | borders do whitespace's job | whitespace first; card only for true containers (§6.F) | | 8 | Centering everything | no anchor line | left-align body; center only short hero lines | | 9 | Cards-in-cards | double padding stacks | flatten to one level; inner groups use spacing | | 10 | Per-child margin-right | phantom trailing gap; breaks wrap | flex; gap on the parent | | 11 | Inconsistent gutters (16/20/24 for one role) | no system | one gutter token per breakpoint | | 12 | Optical blindness (metric-centered glyphs, flush quotes) | looks off-center | §7 | | 13 | Inset ignores surface size (24px on a chip and a panel) | should scale with surface | map inset to surface tier (chip 4–8 → page 32–64) | | 14 | No vertical rhythm (random prose gaps) | off the baseline cadence | gaps = step multiples (§5) | | 15 | Tight display leading on stacked-diacritic text (leading-[0.95] on Vietnamese caps) | tone marks collide between wrapped lines | floor multi-line headings at ≥1.1 for VN / Thai / Arabic / Devanagari (§5.A) | | 16 | Blanket one-column collapse on mobile (.cols-2,.cols-3,.cols-4 { 1fr }) | a card holding one number does not need a phone's width; four of them eat a screen before any content | set columns from the narrowest cell's content demand — stat rows two-up, tables/prose full width (§8.B) | | 17 | Layout property written inline (style={{ gridTemplateColumns: … }}) | outranks every media query, so the responsive rule exists and never fires — silently | inline sets a custom property, CSS keeps the property (§12) |

Magic-number triage: snap 5/6/7→8, 10–15→8/12/16, 17–22→16, 23–26→24. The only sanctioned non-multiples are hairline borders (1px), 0.5px retina rules, and optical nudges ≤4px (typically 1–2px; up to 4px only for large display glyphs). Font-driven values (line-height, cap offsets, derived control insets) are computed, not magic — exempt.

12. IMPLEMENTATION PER STACK

The system is stack-agnostic; the expression is not. One source of truth for spacing per project — if a token system exists, conform; never author a second scale beside it.

| Stack | Native primitive | SPACING_STEP lever | Forbidden | |-------|------------------|--------------------|-----------| | Tailwind v4 | --spacing + p-4/gap-6 | redefine --spacing in @theme | p-[13px], gap-[15px] | | Tailwind v3 | theme.spacing | theme.extend.spacing | arbitrary [13px] | | Plain CSS | --space-* at :root | edit the ramp | hard-coded px in rules | | MUI | theme.spacing(n) (factor 8) | spacing: factor | raw px in sx | | Chakra | space tokens (gap={4}) | extend theme.space | string "13px" props | | Radix Themes | gap/padding props 1–9 | scaling on <Theme> | inline overrides | | shadcn/ui | is Tailwind | --spacing | arbitrary values |

• Tailwind: the default scale is the grid (--spacing = 4px). At SPACING_STEP 8, prefer even steps (2,4,6,8,12). Extend theme.spacing only for named semantic tokens (--spacing-section), never one-off pixels. Own spacing from the parent (gap / space-y-*), not mt-* on every child.
• Plain CSS: declare the ramp once at :root; use logical properties; prefer gap over margins.
• Inline styles outrank every media query — so a layout property written inline has no responsive behaviour at all. A JSX style={{ gridTemplateColumns: '1.5fr 1fr' }} cannot be collapsed by @media (max-width: …), and nothing warns you: the rule is written, the breakpoint fires, the layout does not move. Measured on one app, four dashboards stayed two-column on a phone with the narrow side at 107px, and the collapse rule had been sitting in the stylesheet the whole time. Let the inline set a custom property and keep the property itself in CSS — a variable does not outrank a media query, so the breakpoint stays reachable while a screen can still ask for its own proportions.

css .split { display: grid; grid-template-columns: var(--split-main, 1.5fr) 1fr; } @media (max-width: 760px) { .split { grid-template-columns: 1fr; } } jsx <div className="split" style={{ '--split-main': '1.2fr' }}> {/* not gridTemplateColumns */} Converting a codebase full of these is a judgement per site, not a find-and-replace — the class you move to has to encode §8.B's question, what the narrower cell holds, so you need at least two: one that collapses and one that stays two-up. Sending all of them to the collapsing one reproduces anti-pattern #16. Measured on one sweep: 82 sites, 59 collapse and 23 do not. The same trap covers any inline width, padding, flex-direction or gap. Grep for the property name in markup before trusting a breakpoint: !important "fixes" it and is the wrong tool, because it wins everywhere rather than at the breakpoint you meant.

• Component libs: use the theme transform (theme.spacing(2), gap={4}, Radix scaling), never raw px. shadcn = Tailwind rules.
• Design tokens as SSOT: if tokens.json / Style Dictionary / Figma variables exist, import and reference — if a value isn't in the set, add a named token, don't inline a number. Tokens flow one direction: Figma → Style Dictionary → CSS vars / Tailwind theme → components.

Helper primitives + debugging:

css
.stack  { display:flex; flex-direction:column; gap:var(--space-2); }
.inline { display:flex; align-items:center; gap:var(--space-1); flex-wrap:wrap; }
.grid-auto { display:grid; gap:var(--space-6); grid-template-columns:repeat(auto-fill,minmax(16rem,1fr)); }

* { outline: 1px solid rgba(255,0,0,.25); }   /* surface every box: spot off-scale & uneven gaps */

| Symptom | Likely cause | Fix | |---------|--------------|-----| | gap bigger than spec between siblings | double-owned (parent gap + child margin) | remove the child margin | | inconsistent rhythm down a list | per-child mt/mb | move to container gap | | value not a step multiple | arbitrary px / off-scale token | snap to nearest rung or add a token | | collapsing/overlapping vertical margins | adjacent margin-collapse | switch to gap on a flex/grid parent |

Print & email are distinct spacing environments: @media print — fixed page margins, and snap clamp() section spacing to its MAX (vw is unreliable on paper). HTML email — flex/grid gap is unsupported, so spacing lives on <td> padding + margin (inline-styled); keep one token set.

13. OPERATING PROCEDURE & PRE-FLIGHT CHECKLIST

Run every UI through this loop. Steps 1–4 decide the layout; 5–7 refine; 8 gates the ship. Don't skip because it "looks simple" — the Space Read and dials take seconds.

13.A The pipeline

1. Space Read — one line (§0.B).
2. Set the three dials — explicit STEP / DENSITY / RIGOR (§1).
3. Derive the one scale — generate the ramp from STEP; bind nothing to raw px after this (§2).
4. Lay out — pick the primitive, apply the proximity ladder (§3, §6).
5. Optical pass — fix what the math got geometrically right but visually wrong (§7).
6. Responsive pass — re-evaluate dials per breakpoint; reflow, don't shrink (§8).
7. A11y pass — targets, focus, reflow, text-spacing survival (§9).
8. Pre-flight checklist — every box before output.

13.B Conversational OVERRIDE protocol

The user steers with intent words, not numbers. Map phrase → dial move, re-derive, re-render, restate the new dial line. Never tell the user to edit a file, token, or px — you hold the dials.

| User says | Dial move | |-----------|-----------| | "denser" / "tighter" / "fits more" | DENSITY +2 → gaps down a rung; if ≥7, STEP → 4 | | "more breathing room" / "airier" / "premium" | DENSITY −2 → section gaps up a rung; STEP → 8 | | "cleaner" / "line things up" | RIGOR +2 → lock columns + baseline | | "looser" / "more editorial" | RIGOR −3 → allow optical placement | | "feels cramped" (no density ask) | bump only the violated proximity rung; keep DENSITY | | "looks random / unaligned" | raise RIGOR, snap to grid; don't touch DENSITY |

Override deltas apply to the current dial value and clamp to each dial's [1, 10]; a later override on the same dial supersedes the earlier one.

When to ask: proceed silently when the Space Read completes from the brief. Ask exactly one question only when density intent is genuinely ambiguous and would flip DENSITY by ≥3 (e.g. "marketing hero or in-app dashboard?"). Never ask what you can infer; never ask permission to apply the scale.

13.C Pre-flight checklist

Scale & dials

• ] Three dials stated; SPACING_STEP=4 only if DENSITY ≥ 7.
• ] Every spacing value lands on the ramp — zero magic numbers.
• ] No raw px in markup that bypasses a token.

Rhythm & proximity

• ] Proximity ladder monotonic — no wide gap nested inside a narrow one; tiers differ ≥1.5× (ideally 2×).
• ] label→input < input→nextField.
• ] One gap per container; no per-child margin hacks, no <br>-as-spacer; no double-owned gaps.
• ] Headings asymmetric (above ≈ 2–3× below); consistent section rhythm.

Alignment

• ] Shared left edge for stacked content; columns share tracks at RIGOR ≥ 7; subgrid where card internals must align.
• ] Optical centering applied to asymmetric glyphs/caps; punctuation hangs; numeric columns right/decimal-aligned.
• ] Baseline grid honored where RIGOR ≥ 8.

Responsive

• ] Dials re-evaluated per breakpoint; layout reflows, never shrinks to illegible.
• ] No horizontal scroll at 320px; grids collapse to a stack; 2-D-scroll content isolated in its own container.
• ] Section/component spacing fluid via clamp() with a rem term; safe-area insets on edge-anchored UI.

A11y

• ] Interactive targets ≥ 24×24px (or the 24px-circle spacing exception); 44/48 on touch.
• ] Focus rings visible, unclipped, outline-offset ≥ 2px.
• ] Survives WCAG 1.4.12 text-spacing overrides without clipping or overlap.

Edge cases

• ] Empty / loading / overflow states keep the same rhythm (skeletons match real spacing).
• ] First/last items have correct outer padding (no flush-to-edge unless an intended bleed).
• ] RTL mirrors padding/margins (logical properties).

14. DOCUMENT & LONG-FORM — Word / Google Docs / PDF / Markdown

Written documents (reports, essays, papers, PDFs) obey the same principles — rhythm, measure, proximity, asymmetric headings — through different controls. There is no gap, flex, or px; you set page margins, paragraph spacing, line spacing, and indents in points (pt), inches/cm, or line-spacing multiples. Map the dials: documents are almost always low DENSITY (reading is the job); SPACING_STEP becomes a small pt vertical rhythm (≈6pt); ALIGNMENT_RIGOR governs style consistency and whether body text is justified or left-aligned.

14.A Page setup — margins first

| Doc kind | Margins | Notes | |---|---|---| | Academic (APA / MLA / Chicago) | 1 in / 2.54 cm all sides | with 1.5- or double-spaced body; required, not optional | | Business report | 1 in top/bottom, 1–1.25 in sides | | | Bound / double-sided print | add a gutter (+0.5 in) or use mirror margins | inner edge needs binding room | | Dense reference / handout | 0.75 in | the floor — below this, text crowds the edge |

Choose page size by region — A4 (210×297 mm) vs US Letter (8.5×11 in) — before writing; changing it reflows everything.

14.B Measure — the silent killer in documents

A 12pt body on Letter with 1 in margins is a ~6.5 in line ≈ 90–100 characters, well past the 45–75 ideal (§4.B), so the eye loses the return sweep. Fix with one of: wider margins (1.25–1.5 in), larger type, more leading (double-spacing buys back readability at long measure — why academia mandates it), or two columns. Never ship full-width single-spaced 11pt body.

14.C Line spacing (leading)

The word-processor analog of CSS line-height, set as a multiple on the paragraph style — never via blank lines.

| Use | Line spacing | |---|---| | Body, comfortable | 1.15–1.5 (1.15 floor; 1.5 reads better) | | Academic requirement | 1.5 or 2.0 (double) as specified | | Dense tables / references / footnotes | 1.0–1.08 | | Headings (large) | 1.0–1.1 |

14.D Paragraph spacing & indentation — pick ONE separator

The document single-owner rule (cf. §3.A): a paragraph break is shown by first-line indent OR space-between paragraphs — never both, never neither.

| Style | Separator | Use | |---|---|---| | Indented | first-line indent 0.5 in / 1.27 cm, no space after | books, essays, continuous prose | | Block | space-after 6–10pt (or one line), no indent | business, technical, reports, web |

• Never double-press Enter for paragraph spacing (the document <br><br> — off-rhythm, breaks across pages). Use Spacing After.
• The first paragraph after a heading takes no indent — it needs no separation from the heading it follows.

14.E Heading hierarchy — use styles, space asymmetrically

• Use named styles (Heading 1 / 2 / 3), not manual bold + size — styles give consistent spacing, a navigation pane, and an automatic table of contents.
• Asymmetric spacing (§5.C restated): space-before > space-after, ≈2:1, so the heading bonds to the text below (e.g. H1 24/8 pt, H2 18/6, H3 12/4).
• Enable Keep with next so a heading never strands at the bottom of a page.
• Size steps follow a modular ratio (§2.C): e.g. 11pt body → 14 / 18 / 24pt headings.

14.F Lists, quotes, tables in prose

• Lists: item-to-item spacing tighter than paragraph spacing (one group, §6); nested levels indent one step (0.25–0.5 in); space before/after the whole list = paragraph spacing.
• Block quotes: indent the block (0.5 in), optionally a touch smaller, with space above and below; don't also italicize the whole thing.
• Tables / figures: cell padding ≥ 3–6pt so text doesn't touch the rules; one paragraph of space above/below the table; caption tight to its figure, loose from the next paragraph.

14.G Print & pagination

Turn on Widow/Orphan control (no single line stranded at a page top/bottom), Keep lines together for short blocks, and Page-break-before on major sections (never fake a break with Enter). Keep a consistent header/footer distance from the edge; footnotes get a small space above the separator rule.

14.H Concept → tool mapping

| Concept | CSS / web | Word | Google Docs | Markdown | |---|---|---|---|---| | Line spacing | line-height | Paragraph ▸ Line Spacing | Format ▸ Line & paragraph spacing | (renderer CSS) | | Paragraph spacing | margin / gap | Spacing Before / After | Line & paragraph spacing ▸ Custom | blank line | | First-line indent | text-indent | Ruler / Paragraph ▸ Special | Ruler ▸ first-line indent | — | | Page margins | @page { margin } | Layout ▸ Margins | File ▸ Page setup | — | | Heading | <h1>–<h6> | Styles (Heading 1…) | Styles | # ## ### | | Measure | max-width: 65ch | margins / columns | margins / columns | renderer width | | Page break | break-before | Insert ▸ Page Break | Insert ▸ Break | — |

> Markdown carries no spacing of its own — rhythm comes from the renderer's CSS (§2–§5). Author clean structure (one blank line between blocks, real headings, real lists); style it downstream.

14.I Document pre-flight

• ] Margins set for page size and binding before writing.
• ] Measure 45–75 chars (widen margins / size / spacing / columns if over).
• ] One paragraph separator only — indent or space-after, never both; no double-Enter.
• ] Line spacing ≥ 1.15 (1.5–2.0 if required); set on the style, not by hand.
• ] Headings use named styles; space-before > space-after; Keep-with-next on.
• ] Lists / quotes / tables grouped tighter internally than the surrounding prose.
• ] Widow/orphan control on; major sections start with a real page break.

15. CONTINUOUS IMPROVEMENT — The Field-Learnings Loop

This skill is built to get sharper with use. The sections above are the distilled brain; LEARNINGS.md (repo root) is the raw journal it distills from. After any real spacing/alignment edit, run a short capture-and-distill pass so lessons compound instead of evaporating — the difference between a skill that ages and one that improves.

15.A When it fires

Any edit that creates or changes spacing/alignment on a real artifact — a gap, padding, inset, grid/flex alignment, vertical rhythm, an optical nudge, or a document's margins / leading / indents. Skip pure reading, restating a value that is already on-scale, or a throwaway sketch.

15.B Capture — append one entry to LEARNINGS.md (≈30s)

Date it, newest first. Record the Space Read (surface · dials · the one ratio that mattered), what changed with the real numbers, what the situation taught, and a one-word verdict:

| Verdict | Means | Triggers | |---------|-------|----------| | covered | the skill already prescribed this | nothing — a confirmation | | gap | the skill was silent or wrong here | a §15.C distill pass | | refinement | the skill was right but too vague to act on | a §15.C distill pass |

Log only edits you actually made (ideally saw render). Never invent a lesson you did not hit — evidence, not vibes.

15.C Distill — graduate the lesson into the brain

For a gap / refinement that generalizes past the one case, fold the lesson into the section it belongs to (§0–§14) as a contextual rule, not an anecdote: on-scale, dial-gated, consistent with its neighbors. Then bump CHANGELOG.md (SemVer — new guidance = minor, correction = patch) and prune the graduated entry in LEARNINGS.md to a one-line pointer (→ folded into §n @ vX.Y.Z).

15.D Guardrails

• One datapoint opens a gap; a repeated pattern hardens a default. Don't

rewrite a baseline off a single layout.

• §9 accessibility floors outrank every field preference — a learning may

tighten a gap only down to the floor, never through it.

• Keep the brain lean. The journal grows in LEARNINGS.md; a lesson earns a

place in §0–§14 only by generalizing. Restate in place — never append a second rule that says the same thing.

> Spacing is a system, not a set of nudges — read the layout, name the dials, > derive one scale, and let proximity carry the meaning. Give it room — but give > it measured room.