web-builder

Web Builder

A web builder is a self-contained HTML file with interactive controls on one side, a live preview on the other, and a prompt output at the bottom with a copy button. The user adjusts controls, explores visually, then copies the generated prompt back into Claude.

When to use this skill

When the user asks for an interactive web builder, explorer, or visual tool for a topic — especially when the input space is large, visual, or structural and hard to express as plain text.

How to use this skill

1. Identify the web builder type from the user's request
2. Load the matching template from templates/:
   • templates/sms-composer.md — SMS template composition (message text, quick start, variables, phone preview)
   • templates/preview.md — Message preview (shows personalized messages with template + contacts combined, iMessage-blue phone mockups)
3. Load the global style sheet and component reference from templates/:
   • templates/global-styles.md - Global styles reference
   • templates/component-reference.md - Common html components
4. Follow the template to build the web builder. If the topic doesn't fit any template cleanly, use the one closest and adapt.

Core requirements (every web builder)

• Single HTML file. Inline all CSS and JS. No external dependencies.
• Live preview. Updates instantly on every control change. No "Apply" button.
• Prompt output. Natural language, not a value dump. Only mentions non-default choices. Includes enough context to act on without seeing the web builder. Updates live.
• Copy button. Clipboard copy with brief "Copied!" feedback.
• Sensible defaults + presets. Looks good on first load. Include 3-5 named presets that snap all controls to a cohesive combination.
• Dark theme. System font for UI, monospace for code/values. Minimal chrome.

State management pattern

Keep a single state object. Every control writes to it, every render reads from it.

const state = { /* all configurable values */ };

function updateAll() {
  renderPreview(); // update the visual
  updatePrompt();  // rebuild the prompt text
}
// Every control calls updateAll() on change

Prompt output pattern

function updatePrompt() {
  const parts = [];

  // Only mention non-default values
  if (state.borderRadius !== DEFAULTS.borderRadius) {
    parts.push(`border-radius of ${state.borderRadius}px`);
  }

  // Use qualitative language alongside numbers
  if (state.shadowBlur > 16) parts.push('a pronounced shadow');
  else if (state.shadowBlur > 0) parts.push('a subtle shadow');

  prompt.textContent = `Update the card to use ${parts.join(', ')}.`;
}

Common mistakes to avoid

• Prompt output is just a value dump → write it as a natural instruction
• Too many controls at once → group by concern, hide advanced in a collapsible section
• Preview doesn't update instantly → every control change must trigger immediate re-render
• No defaults or presets → starts empty or broken on load
• External dependencies → if CDN is down, web builder is dead
• Prompt lacks context → include enough that it's actionable without the web builder