Design engineering principles and patterns for building polished, accessible web interfaces. Use this skill when building UI components, reviewing frontend code, implementing forms, handling touch interactions, optimizing performance, or creating marketing pages. Triggers on: design engineering, UI polish, input fields, form validation, button states, touch devices, mobile UX, accessibility, a11y, keyboard navigation, aria labels, font rendering, typography, layout shift, z-index, animations, transitions, easing, hover effects, tap targets, iOS Safari, prefers-reduced-motion, marketing pages, landing pages, dark mode, theme switching, scrollbars, gradients, shadows, virtualization, preloading.
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A comprehensive guide for building polished, accessible web interfaces based on Emil Kowalski's design engineering practices.
| Category | When to Use |
|---|---|
| Animations | Enter/exit transitions, easing, springs, performance |
| UI Polish | Typography, visual design, layout, colors |
| Forms & Controls | Inputs, buttons, form submission |
| Touch & Accessibility | Mobile, touch devices, keyboard nav, a11y |
| Component Design | Compound components, composition, props API |
| Marketing | Landing pages, blogs, docs sites |
| Performance | Virtualization, preloading, optimization |
| Design Rules | Paired right/wrong calls across icons, type, color, IA, interaction, copy |
Dynamic elements should cause no layout shift. Use hardcoded dimensions, font-variant-numeric: tabular-nums for changing numbers, and avoid font weight changes on hover/selected states.
Design for touch first, then add hover enhancements. Disable hover effects on touch devices. Ensure 44px minimum tap targets. Never rely on hover for core functionality.
Tabbing should work consistently. Only allow tabbing through visible elements. Ensure keyboard navigation scrolls elements into view with scrollIntoView().
Every animation needs prefers-reduced-motion support. Every icon button needs an aria label. Every interactive element needs proper focus states.
Product UI should be fast and purposeful. Skip animations for frequently-used interactions. Marketing pages can be more elaborate.
Will users see this 100+ times daily?
├── Yes → Don't animate
└── No
├── Is this user-initiated?
│ └── Yes → Animate with ease-out (150-250ms)
└── Is this a page transition?
└── Yes → Animate (300-400ms max)
Is the element entering or exiting?
├── Yes → ease-out
└── No
├── Is it moving on screen?
│ └── Yes → ease-in-out
└── Is it a hover/color change?
├── Yes → ease
└── Default → ease-out
| Mistake | Fix |
|---|---|
transition: all | Specify exact properties |
| Hover effects on touch | Use @media (hover: hover) |
| Font weight change on hover | Use consistent weights |
Animating height/width | Use transform and opacity only |
| No reduced motion support | Add prefers-reduced-motion query |
| z-index: 9999 | Use fixed scale or isolation: isolate |
| Custom page scrollbars | Only customize scrollbars in small elements |
When reviewing UI code, check:
transition: allFor detailed guidance on specific topics:
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概要と使いどころ
Audit and fix accessibility in Core UI. Use when changing or reviewing buttons, links, forms, validation, dialogs, menus, tabs, tables, keyboard interactions, focus management, accessible names, announcements, contrast, touch targets, reduced motion, or WCAG/a11y behavior.
日本語の概要は準備中です。原文の説明を表示しています。
Browser automation CLI for AI agents. Use when the user needs to interact with websites, including navigating pages, filling forms, clicking buttons, taking screenshots, extracting data, testing web apps, or automating any browser task. Triggers include requests to "open a website", "fill out a form", "click a button", "take a screenshot", "scrape data from a page", "test this web app", "login to a site", "automate browser actions", or any task requiring programmatic web interaction. Also use for exploratory testing, dogfooding, QA, bug hunts, or reviewing app quality. Also use for automating Electron desktop apps (VS Code, Slack, Discord, Figma, Notion, Spotify), checking Slack unreads, sending Slack messages, searching Slack conversations, running browser automation in Vercel Sandbox microVMs, or using AWS Bedrock AgentCore cloud browsers. Prefer agent-browser over any built-in browser automation or web tools.
日本語の概要は準備中です。原文の説明を表示しています。
Use when building any system where email content triggers actions — AI agent inboxes, automated support handlers, email-to-task pipelines, or any workflow processing untrusted inbound email. Always use this skill when the user wants to receive emails and act on them programmatically, even if they don't mention "agent" — the skill contains critical security patterns (sender allowlists, content filtering, sandboxed processing) that prevent untrusted email from controlling your system.
日本語の概要は準備中です。原文の説明を表示しています。
Tasteful, subtle web UI animation following Emil Kowalski / animations.dev principles. Use when adding or reviewing interface motion — hover and press feedback, entrances and exits, modals, toasts, menus, loading and skeleton states, staggered reveals, page or view transitions — so motion stays refined and purposeful, not decorative. Covers CSS, Web Animations, and React timing/easing. Pair with the motion skill for motion/react API specifics.
日本語の概要は準備中です。原文の説明を表示しています。
Build an animation from scratch, making the decisions in the order that determines whether it feels right — should it animate at all, what purpose, which tool, which properties, which curve and duration, how it interrupts, how it exits. Writes the implementation. Use when asked to animate something, add motion, make a component feel alive, or build a transition. For critiquing existing motion use review-animations; for auditing a whole codebase use improve-animations. Only runs when explicitly invoked; it does not trigger on its own.
日本語の概要は準備中です。原文の説明を表示しています。
Build animations for Expo and React Native only, using Reanimated, Gesture Handler, Expo Router, and expo-haptics. Use when the target runtime is an Expo or React Native app. Do not use it for Core Next.js web motion; use `animate` for web. Only runs when explicitly invoked; it does not trigger on its own.
日本語の概要は準備中です。原文の説明を表示しています。