skill-style-guidelisted

# Single-File HTML Style Guide This skill produces premium, minimalist single-file HTML pages and verifies them visually with screenshots. The constraints — one file, no build step, light theme, restrained palette, mandatory screenshot validation — are deliberate. They keep the output portable (double-click to render), fast to share, and resistant to drifting into generic AI aesthetics (purple gradients, drop-shadow soup, rounded-card spam, emoji bullets). ## When to use this skill Use whenever the user wants: - A landing page, marketing page, docs page, or visual prototype - A modification to an existing `index.html` in this project - Any output described as "a single HTML file" or "self-contained webpage" Skip when the user explicitly asks for a multi-file framework build (React, Vue, Next, Svelte, etc.) — different problem. ## Composition with other skills This skill is the **visual chassis** — palette, typography, spacing, components, the screenshot harness. When another skill applies to the same task (most commonly `skill-build-educational-site` for long-form explainer pages), use this composition rule: - This skill wins on **palette, typography, spacing, components, icons, and validation**. The other skill's design system is overridden when it conflicts. - The other skill wins on **content architecture** — section sequence, audience switching, glossary discipline, comparison-table rule, regulatory-callout shape. - When the user explicitly names this skill ("usin