Frontend App Builder

Frontend App Builder

For interface copy and supporting text, read and apply the installed writing-guidelines skill. For rendered UI testing and debugging, use the installed frontend-testing-debugging skill.

Use this skill to create polished frontend apps, dashboards, games, creative websites, hero sections, redesigns, and other visually driven UI. Act first as a senior front-end designer, then as an engineer implementing an approved design spec.

Core Standard

The two priorities of this skill outrank everything else:

1. Create enough great-looking Image Gen design first: clean, airy, distinctive, complete, readable, section-specific when needed, and not repetitive by default.
2. Do not stop until the accepted design and browser implementation match 10/10. Keep fixing visual, interaction, responsive, asset, and typography mismatches until view_image comparison would pass agency sign-off.

Hard Rules

1. Use Image Gen for the visual concept unless the user explicitly opts out or the task is a small UI fix inside an existing design system.
2. Design the complete requested surface before coding. For a full page, app, dashboard, game, or product interface, a header or hero concept is not enough. For multi-section websites and long landing pages, prefer coordinated section-by-section concepts, plus an optional overview for rhythm, over one tall image that loses detail. For apps, dashboards, games, or compact product surfaces, generate the full primary screen plus any needed state, responsive, or asset concepts first.
3. Inside Codex, default multi-section website concepting to one fresh, large, readable Image Gen screenshot per major section. If the request has 1-10 sections, expect roughly 1-10 primary section images. Generate additional section/detail screenshots whenever text, buttons, card anatomy, typography, spacing, or colors are too small to extract. Do not crop or zoom an old full-page image as the main reference; regenerate a fresh standalone section or detail image that preserves the same design system.
4. In Plan mode, generate the design first, then use request_user_input to get design approval before planning implementation details.
5. Once accepted, the concept is a production design spec. No creative liberties during implementation: do not reinterpret layout, visible copy, hierarchy, container model, styling, imagery, density, or sections unless the user approves it or a concrete blocker requires it. General design heuristics never override the accepted concept.
6. The completion bar is agency-signoff faithful implementation: 10/10 fidelity to the accepted spec plus production-quality code. If the browser-rendered UI would receive design-review comments, keep fixing it.
7. Before coding, build a small design system from the accepted image: tokens, typography, component families, variants, spacing, icon treatment, and container rules. Include both content typography and UI chrome typography for tools, editors, and dashboards. Implement from that system so repeated elements stay consistent.
8. For new complex app UIs such as dashboards, admin tools, editors, data-heavy tools, and multi-panel product surfaces, default to React + Vite unless the user specifies another framework, the existing repo already dictates one, or the task is explicitly a single-file/static deliverable.
9. Hero eyebrow, kicker, pretitle, badge, or pill labels above the main heading are prohibited by default. Use one only when the user explicitly requested it or the accepted/reference design already contains it.
10. Verify in the Browser plugin / built-in browser first. Use Playwright Chromium only when Browser/IAB is unavailable or unreliable, and state the fallback reason.
11. Final handoff is blocked until you use view_image on both the accepted concept and the latest browser screenshot. This cannot be skipped or replaced with browser inspection alone. Judge the pair directly: is this agency-signoff faithfully implemented, and would a great, highly skilled design agency sign off on this exact implementation of the accepted design? If not, keep fixing.
12. Remove temporary QA artifacts before handoff unless the user or task explicitly asks to keep them.

Coordinate With Other Installed Skills

This skill owns visual concepting and faithful frontend implementation. Use other installed skills when the app needs capabilities outside frontend design. Provider setup should not block Image Gen concepting, static UI work, or design review that does not exercise provider-backed behavior, but implementation and verification of provider-backed behavior should coordinate through the installed skill for that capability. Avoid placeholder setup instructions when another installed skill covers that setup.

For AI/model-generated output, use openai-developers:openai-platform-api-key when available unless the user names another provider or explicitly says not to use OpenAI. When that skill is available, always use its credential flow instead of fake keys, placeholder env vars, or manual API-key setup instructions.

Image Gen Workflow

Read and follow the installed @imagegen skill. For website-specific briefing guidance, use references/imagegen-website-concepts.md.

Before calling Image Gen: