Use when producing specs, plans, research notes, reports, code reviews, design explorations, or interactive editors that the user will read end-to-end. Default to a single self-contained HTML file with inline CSS and (when needed) inline JS, following the Anthropic-style design system extracted from Thariq's html-effectiveness gallery. Skip this skill for short conversational replies, simple commands, or markdown source files in code repos where diff reviewability matters more than render quality.
