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.
npx skills add flitzrrr/frontend-design-skills --skill responsive-designgit clone --depth 1 https://github.com/flitzrrr/frontend-design-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/flitzrrr/frontend-design-skills/responsive-design)<a href="https://agentmods.dev/skills/flitzrrr/frontend-design-skills/responsive-design"><img src="https://agentmods.dev/badge/skills/flitzrrr/frontend-design-skills/responsive-design/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/flitzrrr/frontend-design-skills/responsive-design"><img src="https://agentmods.dev/badge/skills/flitzrrr/frontend-design-skills/responsive-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00032 | $0.01576 |
| Opus 5 | $0.00016 | $0.00788 |
| Sonnet 5 | $0.00006 | $0.00315 |
| Haiku 4.5 | $0.00003 | $0.00158 |
Grade A, and why
responsive-design 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 9d 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.
How it starts
The opening of the file, as written. The whole thing — 163 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Responsive Design
Start with the smallest viewport and the most important content. Enhance progressively. If it doesn't work at 320px, it has no place at 1920px.
Scope
Use this skill when you:
- Design a layout for different viewports and devices
- Define or review breakpoints
- Implement mobile-first CSS strategies
- Implement responsive images and media
- Need to ensure touch optimization
- Set up responsive typography
Principles
1. Mobile First, Content First
Start with the smallest viewport and the most important content. Enhance progressively for larger screens.
2. Content Determines Breakpoints
Set breakpoints where the design breaks — not at device widths. "Start with the small screen first, then expand until it looks like shit. Time for a breakpoint!" (Stephen Hay).
3. Flexibility Over Perfection
Websites don't need to be pixel-perfect. They need to look good and be usable on every device.
4. Four Building Blocks
Responsive design consists of flexible layout, media queries, flexible media, and flexible typography.
5. Content Choreography
Content adapts not only in size but in arrangement, prioritization, and presentation to match the viewport.
6. Progressive Enhancement
Build a solid foundation for all devices and enhance progressively for more capable systems.
Rules
DO: Use a Fluid Grid
- USE percentage-based widths instead of fixed pixel values.
- USE CSS Grid for two-dimensional layouts, Flexbox for one-dimensional layouts.
- SET a max-width for the overall container (e.g., 1200-1440px).
- PREFER a 12-column grid system as the starting point.
DO: Implement Mobile-First in CSS
- WRITE base CSS for the smallest viewport.
- EXTEND with
min-widthmedia queries for larger screens. - AVOID
max-widthmedia queries as the primary strategy (that is desktop-first).
DO: Implement Responsive Images
- USE
srcsetwith at least 3 image sizes (400px, 800px, 1200px). - USE the
pictureelement for art direction. - SET
widthandheightattributes to prevent CLS. - IMPLEMENT
loading="lazy"for images below the fold. - COMPRESS in WebP or AVIF.
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.
- 9d ago First seen · 163 lines · 32 tokens per session scan A 4e89e3812573
responsive-design is a skill published in the GitHub repository flitzrrr/frontend-design-skills (5 stars, last pushed 5mo ago), licensed MIT. It adds 32 tokens to every session and 1,576 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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