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v0.1 · 2026-04-28

Rhythm

Rhythm is how predictably elements repeat across a Vaquum surface. Three values; the third names the failure state.

What rhythm is

Rhythm is the predictability of repetition on a Vaquum surface. Three values close the parameter: uniform, varied, and arrhythmic. Each value declares a permitted distribution of gap values, body element sizes, and vertical axes. The exhibit below renders one illustrative gap-share distribution per value as a histogram, with the typed thresholds from @vaquum/face/parameters/rhythm overlaid.

Three values

A uniform surface holds at least 80 percent of its sibling-to-sibling gaps at one dominant value. The body carries a single repeating element size and a single vertical axis. A varied surface presents two-to-three gap values, each above 10 percent of the total, and admits two-to-three body element sizes on the same vertical axis. An arrhythmic surface declares either more than three distinct gap values or a dominant value below 10 percent. The closed set names the failure so the validator can report it.

How rhythm is measured

Gap variation is measured as the distribution of vertical-gap values across every sibling-to-sibling transition on the rendered surface. Element-size variation is measured on body-level elements — paragraph, figure, table — excluding headings and metadata. Axis displacement is measured as the number of distinct horizontal starting positions used by block-level elements. The three measures are independent, and a surface must satisfy each of them to satisfy its rhythm.

How rhythm composes with proportion

Proportion sets the closed set of permitted gap values; rhythm governs how predictably the chosen members of that set recur. A surface declared proportion: standard draws its gaps from the set 16, 24, 64 px, and rhythm names which subset is read as dominant. The two parameters are independent, and a surface must hold both at once. Adding a fourth gap value violates proportion before it ever reaches rhythm.

The arrhythmic failure state

Arrhythmic exists in the closed set so the validator can name what has gone wrong. A surface that declares it has crossed into a typography the firm does not produce — gaps unrecognisable as a system, body sizes proliferating, blocks displaced from their column. The validator measures rhythm at the rendered DOM and emits a failure the moment any of the three distributions falls outside the bracket the surface declared.

face · rhythm · 3 illustrative distributions · small multiples

uniform

0% 50% 100% 1 2 3 dominance floor 80% distinct gap value share of gaps
One gap value carries 85 percent of the gaps; the rest take incidental presence above the dominance floor.

varied

0% 50% 100% 1 2 3 presence floor 10% distinct gap value
Three gap values share the surface, each held above the per-value presence floor.

arrhythmic

0% 50% 100% 1 2 3 4 5 6 7 8 distinct gap value
Eight gap values present — the count rises above the rule of three; the surface earns a composition failure.

Each histogram is one illustrative distribution that satisfies its rhythm bracket; the canon specifies the bracket rule, not the distribution. Accent rules read from `@vaquum/face/parameters/rhythm` mark the dominance floor uniform requires and the per-value presence floor varied requires. Arrhythmic carries no such horizontal threshold — its failure registers in the gap-value count rising above three.