pseudo-elements
Audit CSS for pseudo-element best practices and View Transitions API usage. Use when reviewing hover effects, decorative layers, or page transitions. Outputs file:line findings.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/raphaelsalaja/skill --skill pseudo-elements- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads pseudo-elements automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Pseudo Elements
Review CSS and JavaScript for pseudo-element best practices and View Transitions API usage.
How It Works
- Read the specified files (or prompt user for files/pattern)
- Check against all rules below
- Output findings in
file:lineformat
Rule Categories
| Priority | Category | Prefix |
|---|---|---|
| 1 | Before/After | pseudo- |
| 2 | View Transitions | transition- |
| 3 | Native Styling | native- |
Rules
Before/After Rules
pseudo-content-required
::before and ::after require content property to render.
Fail:
.button::before {
position: absolute;
background: var(--gray-3);
}
Pass:
.button::before {
content: "";
position: absolute;
background: var(--gray-3);
}
pseudo-over-dom-node
Use pseudo-elements for decorative content instead of extra DOM nodes.
Fail:
<button className={styles.button}>
<span className={styles.background} /> {/* Unnecessary DOM node */}
Click me
</button>
Pass:
<button className={styles.button}>
Click me
</button>
.button::before {
content: "";
/* decorative background */
}
pseudo-position-relative-parent
Parent must have position: relative for absolute pseudo-elements.
Fail:
.button::before {
content: "";
position: absolute;
inset: 0;
}
/* .button has no position */
Pass:
.button {
position: relative;
}
.button::before {
content: "";
position: absolute;
inset: 0;
}
pseudo-z-index-layering
Pseudo-elements need z-index to layer correctly with content.
Fail:
.button::before {
content: "";
position: absolute;
inset: 0;
background: var(--gray-3);
}
/* Covers button text */
Pass:
.button {
position: relative;
z-index: 1;
}
.button::before {
content: "";
position: absolute;
inset: 0;
background: var(--gray-3);
z-index: -1;
}
pseudo-hit-target-expansion
Use negative inset values to expand hit targets without extra markup.
Fail:
<div className={styles.wrapper}> {/* Extra wrapper for hit target */}
<a className={styles.link}>Link</a>
</div>
Pass:
.link {
position: relative;
}
.link::before {
content: "";
position: absolute;
inset: -8px -12px;
}
View Transitions Rules
transition-name-required
Elements participating in view transitions need view-transition-name.
Fail:
document.startViewTransition(() => {
// No view-transition-name assigned
targetImg.src = newSrc;
});
Pass:
sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
sourceImg.style.viewTransitionName = "";
targetImg.style.viewTransitionName = "card";
});
transition-name-unique
Each view-transition-name must be unique on the page during transition.
Fail:
.card {
view-transition-name: card;
}
/* Multiple cards with same name */
Pass:
// Assign unique name only to transitioning element
element.style.viewTransitionName = `card-${id}`;
transition-name-cleanup
Remove view-transition-name after transition completes.
Fail:
sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
targetImg.style.viewTransitionName = "card";
});
// sourceImg still has name, causes conflict on next transition
Pass:
sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
sourceImg.style.viewTransitionName = "";
targetImg.style.viewTransitionName = "card";
});
transition-over-js-library
Prefer View Transitions API over JavaScript animation libraries for page transitions.
Fail:
import { motion } from "motion/react";
function ImageLightbox() {
return (
<motion.img layoutId="hero" /> // JS-based shared element transition
);
}
Pass:
function openLightbox(img: HTMLImageElement) {
img.style.viewTransitionName = "hero";
document.startViewTransition(() => {
// Native browser transition
});
}
transition-style-pseudo-elements
Style view transition pseudo-elements for custom animations.
Fail:
document.startViewTransition(() => { /* ... */ });
// Uses default crossfade
Pass:
::view-transition-group(card) {
animation-duration: 300ms;
animation-timing-function: cubic-bezier(0.215, 0.61, 0.355, 1);
}
Native Styling Rules
native-backdrop-styling
Use ::backdrop pseudo-element for dialog/popover backgrounds.
Fail:
<>
<div className={styles.overlay} onClick={close} />
<dialog className={styles.dialog}>{children}</dialog>
</>
Pass:
dialog::backdrop {
background: var(--black-a6);
backdrop-filter: blur(4px);
}
native-placeholder-styling
Use ::placeholder for input placeholder styling, not wrapper elements.
Fail:
<div className={styles.inputWrapper}>
{!value && <span className={styles.placeholder}>Enter text...</span>}
<input value={value} />
</div>
Pass:
input::placeholder {
color: var(--gray-9);
opacity: 1;
}
native-selection-styling
Use ::selection for text selection styling.
Pass:
::selection {
background: var(--blue-a5);
color: var(--gray-12);
}
Output Format
When reviewing files, output findings as:
file:line - [rule-id] description of issue
Example:
components/button/styles.module.css:12 - [pseudo-content-required] ::before missing content property
components/lightbox/index.tsx:45 - [transition-over-js-library] Using motion layoutId instead of View Transitions API
Summary Table
After findings, output a summary:
| Rule | Count | Severity |
|---|---|---|
pseudo-content-required | 2 | HIGH |
pseudo-over-dom-node | 1 | MEDIUM |
transition-name-cleanup | 1 | MEDIUM |
References
FAQ
What does the pseudo-elements skill do?
Audit CSS for pseudo-element best practices and View Transitions API usage. Use when reviewing hover effects, decorative layers, or page transitions. Outputs file:line findings.
How do I install pseudo-elements?
Run npx skills add https://github.com/raphaelsalaja/skill --skill pseudo-elements in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/pseudo-elements/ (personal) or .claude/skills/pseudo-elements/ (project).
Which AI agents can use pseudo-elements?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is pseudo-elements safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains pseudo-elements?
It is published by raphaelsalaja in raphaelsalaja/skill. It has 247 recorded installs.
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