css-expert

A guide to modern CSS, the language that controls the layout and appearance of web pages. It covers tools for arranging items in rows, columns, and responsive layouts that adapt to different screen sizes.

In plain words
What is it for?
Use it to build or troubleshoot page layouts, responsive interfaces, themes, animations, and reusable design styles with CSS.
Why use it?
It helps solve layout problems such as inconsistent spacing, difficult responsive behavior, and styles that are hard to maintain. It also encourages reusable values and more predictable style rules.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/ginkida/rustyhand/css-expert
Any agent
npx skills add ginkida/rustyhand --skill css-expert
Clone the repo
git clone --depth 1 https://github.com/ginkida/rustyhand

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 624 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00021 $0.00624
Opus 5 $0.00010 $0.00312
Sonnet 5 $0.00004 $0.00125
Haiku 4.5 $0.00002 $0.00062

Measured 2d ago against content hash ca02c989abda, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

css-expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to css-expert — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

crates/rusty-hand-skills/bundled/css-expert/SKILL.md · 40 lines

How it starts

The opening of the file, as written. The whole thing — 40 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CSS Expert

A front-end layout specialist with deep command of modern CSS, from flexbox and grid to container queries and cascade layers. This skill provides precise, standards-compliant guidance for building responsive, accessible, and maintainable user interfaces using the latest CSS specifications and best practices.

Key Principles

  • Use flexbox for one-dimensional layouts (rows or columns) and CSS Grid for two-dimensional layouts (rows and columns simultaneously)
  • Embrace custom properties (CSS variables) for theming, spacing scales, and any value that repeats or needs runtime adjustment
  • Design mobile-first with min-width media queries, layering complexity as viewport size increases
  • Prefer logical properties (inline-start, block-end) over physical ones (left, bottom) for internationalization-ready layouts
  • Leverage the cascade intentionally with @layer declarations to control specificity without resorting to !important

Techniques

  • Use flexbox justify-content and align-items for main-axis and cross-axis alignment; flex-wrap with gap for fluid card layouts
  • Define CSS Grid layouts with grid-template-areas for named regions, and auto-fit/auto-fill with minmax() for responsive grids without media queries
  • Create design tokens as custom properties on :root (--color-primary, --space-md) and override them in scoped selectors or media queries
  • Use @container queries to style components based on their parent container size rather than the viewport
  • Build animations with @keyframes and animation shorthand; prefer transform and opacity for GPU-accelerated, jank-free motion
  • Apply transitions on interactive states (hover, focus-visible) with appropriate duration (150-300ms) and easing functions
  • Use the :has() selector for parent-aware styling, :is()/:where() for grouping selectors with controlled specificity

Common Patterns

  • Holy Grail Layout: CSS Grid with grid-template-rows (auto 1fr auto) and grid-template-columns (sidebar content sidebar) for header/footer/sidebar page structures
  • Fluid Typography: clamp(1rem, 2.5vw, 2rem) for font sizes that scale smoothly between minimum and maximum values without breakpoints
  • Aspect Ratio Boxes: Use the aspect-ratio property directly instead of the legacy padding-bottom hack for responsive media containers
  • Dark Mode Toggle: Define color tokens as custom properties, swap them inside a prefers-color-scheme media query or a data-theme attribute selector

Read the full file on GitHub · 40 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 40 lines · 21 tokens per session scan A ca02c989abda

Subscribe to this mod's changes

css-expert is a skill published in the GitHub repository ginkida/rustyhand (20 stars, last pushed 22d ago), licensed MIT. It adds 21 tokens to every session and 624 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to css-expert, differing in 0 lines, and is treated as a copy.

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