Glossary

Terms used throughout the docs.

Atomic CSS — A CSS architecture where each (property, value, selector) combination produces exactly one class. Traditional CSS produces one class per component; atomic CSS produces one class per unique declaration. See Thinking in atomic CSS.

Auto-dark mode — Compiler pass that derives a dark-mode counterpart of every color value in your styles, using HSL inversion + WCAG-AA contrast adjustment. See Dark mode.

Auto-RTL — Compiler pass that rewrites physical CSS properties (marginLeft, paddingRight, etc.) to their logical equivalents (marginInlineStart, paddingInlineEnd, etc.). See RTL.

Class meta — The __TRACELESS_STYLE_META__ constant injected via DefinePlugin. Maps each emitted class name to the property it controls; used by tl.merge for last-wins conflict resolution.

Container query variant — A variant whose selector uses @container (...) instead of @media (...). Adapts to the parent's width, not the viewport's. See _containerSm/_containerMd/_containerLg.

Custom variant — A variant registered via tl.extend({ variants: ... }). Discovered by Pass 1 of the compiler.

defineTokens — tl.defineTokens(map). Compiles to :root { --tl-<hash>: value; } for each leaf and returns a typed nested object whose leaves are var(--tl-<hash>) strings.

Extractor — The build-time component that scans source files, finds tl.create/tl.extend/tl.defineTokens/tl.createTheme/tl.keyframes calls, and registers atomic rules. Two implementations: extractor.ts (legacy, text-mode) and extractor-swc.ts (SWC AST). Both expose the same interface.

FNV-1a — The hash algorithm used to produce 8-char base36 class names. Two parallel 32-bit FNV-1a streams combined via BigInt. See Hashing.

globalRegistry — Module-level singleton in src/compiler/extractor.ts that accumulates atomic rules across an extraction run. Cleared at the start of each full run.

Hash invariant — The runtime↔compiler↔tokens module must produce byte-for-byte identical hashes for identical inputs. Pinned by test/hash.test.ts and test/tokens.test.ts.

Lint rule — Strict-by-default code rules: no-inline-styles, no-class-string, no-css-modules, no-tailwind. See Linting.

Logical property — CSS property whose meaning depends on the writing direction (marginInlineStart resolves to marginLeft in LTR and marginRight in RTL). The auto-RTL compiler pass rewrites physical properties to logical.

Pass 0 / 1 / 2 — The three sweeps the extractor makes over source files. Pass 0 collects token exports; Pass 1 collects custom variants; Pass 2 transforms tl.create calls. See Two-pass extraction.

Property allowlist — ~250 curated CSS properties accepted by tl.create. Anything else triggers a Levenshtein-suggested error. See src/compiler/css-properties.ts and Property allowlist.

tlXXXXXXXX — 10-character class name pattern: literal tl prefix + 8-character base36 FNV-1a hash. See Hashing.

tlKfXXXXXXXX — 12-character keyframe-name pattern: literal tlKf prefix + 8-character hash of "keyframes:" + name.

tlThemeXXXXXXXX — 15-character theme-class pattern: literal tlTheme prefix + 8-character hash of "theme:" + name.

Token export registry — Per-file map populated by Pass 0 of the extractor. Maps export name → nested token shape, so cross-file token references resolve correctly. See Cross-file resolution.

TracelessClass — Branded class-name string type. Component props typed as className?: TracelessClass reject bare strings unless explicitly cast.

TracelessStyleWebpackPlugin — The webpack plugin that runs full extraction on beforeCompile, injects __TRACELESS_STYLE_META__ via DefinePlugin, and re-emits CSS on afterEmit.

Variant — A name (e.g. _hover, sm, _dark) that maps to a CSS selector or @-rule. Used to attach conditional styles inside tl.create. See Variants.

WCAG contrast audit — Build-time check that every color/background pair passes WCAG 2.1 AA (4.5:1 normal / 3:1 large) or AAA (7:1 / 4.5:1). See WCAG contrast validation.

Zero-runtime — No client-side cost beyond a tiny pure helper module. The library does no DOM mutation, no style-element insertion, no cache lookup against an atomic registry. The runtime is functional code over strings.