HTML Mockup Prototyping

Overview

Single-file HTML prototypes using Tailwind CDN + Alpine.js. Open in a browser — no build step, no server, no framework. Best for exploring flows and interaction states quickly.

Stack: Tailwind CSS (utility styling) + Alpine.js (declarative state/behavior) + Lucide (icons). All load from CDN.

When to Use

• Design is unclear and needs visual exploration before a proposal or plan
• Feature has multiple states (loading, success, error, empty) that need to be shown
• Stakeholder needs to review a flow before implementation begins
• UX patterns are undecided (e.g., single-step vs multi-step upload)

Not for:

• Production code or anything that will be committed to the app
• Complex data-driven interactions (use the real UI for that)

Starter Templates

Two templates are available in templates/:

• state-flow.html — flat single-row switcher. Use for a single flow with up to ~7 states (e.g., idle → loading → success → error).
• group-state-flow.html — two-level group/state switcher. Use when covering multiple related flows or tabs in one file (e.g., a multi-tab admin UI, all auth flows, or any feature with named sections each having sub-states).

Both include the full theme block, CDN imports (Tailwind, Alpine.js, Lucide), Alpine.data() registration pattern, Lucide initialization with debounced MutationObserver, and a blank content area with placeholder states to replace.

The content area is yours to fill. Sidebar nav, single column, split pane — whatever the prototype needs.

Theme Classes

The template provides semantic classes so markup stays readable. Use these instead of raw Tailwind utility strings:

Category	Classes
Typography	page-title, section-title, label, text-body,
	text-muted, text-faint, text-mono, link
Surfaces	card, inset, panel-section
Badges	badge-accent, badge-muted, badge-warning
Status	status-dot-open, status-dot-success
Buttons	btn-primary, btn-outline, btn-ghost, btn-icon
Forms	input, select, textarea, input-error, field-error
Alerts	alert-error, alert-success, alert-info, alert-warning
Navigation	nav-item, nav-item-active, nav-item-inactive
Utilities	filter-pill, skeleton (loading shimmer)

Add new semantic classes to the theme block as needed — follow the same @apply pattern. Keep raw Tailwind for one-off layout utilities (flex, padding, gap, etc.).

Theme Adaptation

Before building, check if the target project has a theme file (CSS variables, Tailwind config, shadcn theme, etc.). If one exists, ask the user whether the prototype should reflect the app's look. If yes, adapt the template's theme block to approximate the app's color palette and general feel.

Keep it lightweight — the goal is visual correspondence, not pixel-perfect reproduction. Swap the slate palette for the project's colors, adjust accent colors, match light/dark mode. The semantic class names stay the same; only the @apply definitions change.

Light theme note: Adapting to a light theme touches almost every class in the theme block — it's a near-complete rewrite of all @apply definitions, not just a palette swap. Base colors, surface colors, text colors, borders, and component states all need adjustment. Plan accordingly, or start from a light-theme variant rather than modifying the dark default.

Lucide Icons

Lucide provides 1500+ consistent SVG icons via CDN. Use them for nav items, buttons, status indicators, and anywhere text alone is ambiguous.

Usage: <i data-lucide="icon-name" class="w-4 h-4"></i> — the template's MutationObserver handles initialization, including icons inside x-show/x-if blocks.

Sizing: w-3 h-3 (12px), w-4 h-4 (16px — default), w-5 h-5 (20px), w-6 h-6 (24px).

Color: Icons inherit currentColor — Tailwind text color classes work directly.

Common icons:

Category	Icons
Navigation	menu, x, chevron-right, chevron-down, arrow-left
Actions	plus, pencil, trash-2, download, upload, search
Status	check, check-circle, alert-triangle, alert-circle, x
Objects	file-text, folder, image, link, settings, user
UI chrome	bell, layout-dashboard, shield, eye, eye-off, loader

Browse all icons at lucide.dev/icons.

Flow Design Process

1. List states first — write out every distinct screen/state before touching HTML (e.g., idle → analyzing → populated → uploading → success)
2. Build the state switcher — wire up all states even if some are placeholders; label each N · Description
3. Fill most important states — happy path first, then edge cases
4. Add realistic app chrome — match the actual context of the page. For dashboard/admin flows: sidebar nav + top header. For auth flows, settings forms, and onboarding: a plain background + centered card IS the shell. The goal is visual context, not always a nav bar.
5. Review with user — click through states; iterate on design before committing to a plan

Key Conventions

State switcher — Always the amber bar at top. This is what makes it a flow mockup vs. a static screenshot. For single flows (up to ~7 states), use a flat button list. For multi-flow mockups with closely related flows, use the two-level switcher:

• Row 1: group tabs (flow names, e.g. "Sign In", "Sign Up", "Account Settings")
• Row 2: state buttons for the active group only
• Groups and states declared as data in Alpine.data() — markup stays clean with x-for and a get activeGroup() computed property

<!-- Row 1: group tabs -->
<div class="px-4 pt-2 pb-0 flex items-center gap-1">
  <template x-for="g in groups" :key="g.id">
    <button
      @click="selectGroup(g.id)"
      :class="group === g.id ? 'bg-amber-700/60 text-amber-100 border-amber-600/60' : 'text-amber-400/70 border-transparent hover:text-amber-300 hover:bg-amber-800/30'"
      class="text-xs px-3 py-1.5 rounded-t border border-b-0 font-medium transition-colors"
      x-text="g.label"
    ></button>
  </template>
</div>
<!-- Row 2: state buttons for active group -->
<div class="px-4 py-1.5 flex items-center gap-1.5 bg-amber-900/30">
  <template x-for="s in activeGroup.states" :key="s.id">
    <button
      @click="selectState(s.id)"
      :class="state === s.id ? 'bg-amber-600 text-white border-amber-600' : 'bg-slate-800 text-slate-300 border-slate-600'"
      class="text-xs px-2.5 py-1 rounded border font-medium transition-colors"
      x-text="s.label"
    ></button>
  </template>
</div>

See templates/group-state-flow.html for a self-contained working starting point with 3 placeholder groups and 7 states.

Realistic shell — Wrap the mockup in app chrome. Avoids "floating widget" syndrome where design looks good in isolation but context is unclear.

File location — Ask the user where they'd like the mockup saved. Common patterns: project artifacts folder, a mockups/ directory, or alongside the feature code. Name the file descriptively (e.g., upload-flow-mockup.html).

Resist real logic — Buttons should just set state = 'next', not implement actual behavior. The goal is to show what happens, not make it work.

Common Mistakes

• Too many states in one file — for a single linear flow, keep to ~6-7 states so reviewers don't get lost. When covering multiple closely related flows (e.g., all auth flows), use the two-level switcher to organize them in one file — the real constraint is reviewability, not a hard count. Split into separate files only when flows are unrelated or the file becomes unwieldy.
• Missing the state switcher — without it, reviewers can only see one state.
• No app chrome — floating a form on a white page makes layout decisions ambiguous.
• Skipping states — build all states (including error/empty) early, even as placeholders. This is where the most valuable design decisions happen.
• Lucide + MutationObserver infinite loop — calling lucide.createIcons() inside a raw MutationObserver callback creates an infinite loop: icons modify DOM → observer fires → icons modify DOM again. Always debounce with requestAnimationFrame as shown in the template.
• $watch in x-init for state switcher setup — using $watch('state') to auto-configure demo states (e.g., selecting a user when switching to "user-selected") causes cascading reactive updates that can freeze the page. Instead, put setup logic directly in the state button's @click handler: @click="state = 'user-selected'; selectedUser = users[0];".
• x-if on table rows — wrapping <tr> elements in <template x-if> can break table column alignment because the conditional rows render in a separate DOM context. Use x-show on <tr> elements instead — they stay in the same table structure and columns align correctly.
• x-for inside <tbody> — placing <template x-for> inside <tbody> causes an importNode TypeError. The browser HTML parser strips <template> tags when nested inside <tbody>, giving Alpine a null template.content. Fix: put the <tbody> inside the x-for template — <table> can have multiple <tbody> elements. See references/tables.html for a working demo.
• Object.entries() destructuring in x-for — using [key, val] in Object.entries(obj) causes "X is not defined" ReferenceErrors. Use Object.keys(obj) and access values with obj[key] bracket notation. See references/tables.html for a working demo.
• SVG/icon pointer events breaking @click handlers — When Lucide replaces an <i> with an <svg>, the SVG and its inner <path> elements become real DOM nodes that receive pointer events. Clicking directly on the icon means the event target is the <svg> or <path>, not the button. Alpine's handler can fail to fire or behave unexpectedly when .stop or other modifiers are involved. Fix: add pointer-events-none to any icon inside a clickable element with an Alpine event handler.

  <!-- ✅ correct -->
  <button @click="doSomething()">
    <i data-lucide="trash-2" class="w-4 h-4 pointer-events-none"></i>
  </button>
  

  This applies to buttons, list items, dropdown triggers, or any interactive element where you're relying on the parent to handle the click.
• overflow-hidden clipping dropdowns and tooltips — the .card class includes overflow-hidden which clips absolutely-positioned children like dropdown menus, custom selects, and tooltips. Use !overflow-visible on cards that contain these components, or move the popover element outside the card container.
• Inline x-data with complex state — large inline x-data objects cause Alpine.js parsing errors. Always use the Alpine.data() registration pattern in the template's script block.

Pattern References

Runnable mini-mockups demonstrating solutions to specific Alpine.js / HTML problems. See references/index.md for the full list.

Pattern	File
Tables with x-for / Object.keys	references/tables.html
Two-level group/state switcher	templates/group-state-flow.html
UI components (toggle, switch, modal, tags, etc.)	references/components.html

Skill Feedback

If anything in this skill was unclear, didn't work as expected, or could be improved, write a skill_feedback.md file alongside the mockup output. Keep it brief — a sentence or two is enough. Only do this if you have something genuinely useful to report; don't force it.

## Skill Feedback
- [What was confusing or broken]
- [What would have helped]

This helps the skill evolve based on real usage.