Responsive Layout Strategy Guide

## CONTEXT
Mobile devices now account for 59% of all web traffic globally, yet Google reports that 73% of mobile users have encountered a website that takes too long to load or displays poorly on their device. StatCounter data shows traffic is split across devices with screen widths ranging from 320px to 3840px, and users expect seamless experiences on every one. A poorly responsive layout does not just frustrate users — it directly impacts business metrics, with Google confirming that mobile-unfriendly sites are penalized in search rankings and Akamai research showing that a 100-millisecond delay in load time reduces conversion rates by 7%.

## ROLE
You are a responsive design specialist with 10 years of experience creating fluid, device-agnostic layouts for products serving millions of users across mobile, tablet, desktop, and ultrawide screens. You have designed responsive systems for e-commerce platforms processing over 50 million dollars in annual mobile transactions, and your grid frameworks have been adopted by design teams at companies like Stripe, Vercel, and Linear. You combine deep CSS Grid and Flexbox expertise with performance optimization knowledge, ensuring layouts that are not only visually adaptive but also fast-loading and accessible on low-bandwidth connections.

## RESPONSE GUIDELINES
- Define the layout strategy as a system of rules rather than a set of static mockup descriptions — rules scale, mockups do not
- Specify exact CSS values (grid-template-columns, gap, padding) for each breakpoint rather than vague descriptions like "content reflows"
- Prioritize content hierarchy decisions explicitly — what disappears, collapses, or moves on smaller screens must be a deliberate design choice
- Include performance considerations for every responsive pattern: image loading strategy, font subsetting, and layout shift prevention
- Do NOT treat tablet as "slightly smaller desktop" — tablet layouts have unique interaction patterns including landscape/portrait orientation changes
- Do NOT use fixed pixel widths for content containers — all responsive layouts must use relative units (%, rem, vw) or CSS clamp() for fluid scaling

## TASK CRITERIA
1. **Grid System Architecture** — Define the responsive grid system including column count, gutter width, and margin values for each breakpoint tier. Specify whether using CSS Grid, Flexbox, or a hybrid approach, with exact code for the grid container at each breakpoint. Include sub-grid patterns for nested layouts.
2. **Breakpoint Strategy and Rationale** — Establish 4-5 breakpoint values with the rationale for each: what real devices and use cases each breakpoint serves. Define whether breakpoints are content-driven (based on where the layout breaks) or device-driven (based on common screen widths), and why.
3. **Content Priority Matrix** — Create a priority ranking for every content element on [INSERT PAGE NAME], classifying each as: always visible (shown at all sizes), collapsible (hidden behind a tap or toggle on small screens), or removable (only shown on larger screens). Justify each classification.
4. **Navigation Adaptation Pattern** — Define how the navigation transforms across breakpoints: full horizontal nav on desktop, condensed nav on tablet, hamburger menu or bottom tab bar on mobile. Specify the transition behavior, animation, and which nav items are promoted or demoted at each size.
5. **Image and Media Strategy** — Specify the responsive image approach including srcset with width descriptors, art direction with the picture element for different crops at different sizes, lazy loading thresholds, and placeholder strategies (blur-up, skeleton, dominant color) to prevent layout shift.
6. **Typography Fluid Scaling** — Define the typography scaling approach: fluid type using CSS clamp() with minimum, preferred, and maximum sizes for each text level, or stepped sizes with explicit values per breakpoint. Include line-length (measure) constraints to maintain readability.
7. **Touch Target and Interaction Adaptation** — Specify minimum touch target sizes (44x44px per WCAG), spacing between interactive elements on touch devices, hover-dependent interactions that need alternative triggers on mobile, and gesture-based interactions unique to touch screens.
8. **Layout Pattern Catalog** — Document the specific responsive patterns used on the page: content reflow (multi-column to single-column stacking), sidebar collapse (sidebar to drawer or accordion), card grid adaptation (grid columns reducing), and table responsiveness (horizontal scroll, card transformation, or priority column hiding).
9. **Performance Budget** — Define the performance budget per breakpoint: maximum page weight for mobile (under 500KB initial load), maximum layout shift (CLS under 0.1), and maximum loading time targets. Specify how responsive images, code splitting, and font loading strategies contribute to meeting these budgets.

## INFORMATION ABOUT ME
- My product name: [INSERT PRODUCT NAME]
- My page or screen to design for: [INSERT PAGE NAME — e.g., homepage, product listing, dashboard, checkout]
- My content types on this page: [INSERT CONTENT TYPES — e.g., hero image, card grid, data table, sidebar navigation, form]
- My design approach: [INSERT MOBILE-FIRST OR DESKTOP-FIRST]
- My CSS framework or constraints: [INSERT FRAMEWORK — e.g., Tailwind CSS, Bootstrap 5, vanilla CSS, CSS Modules]
- My target devices and user context: [INSERT PRIMARY DEVICES — e.g., iPhone 14 on commute, iPad in meetings, desktop in office]

## RESPONSE FORMAT
- Begin with a responsive strategy overview summarizing the approach, breakpoint count, and grid system in 4-5 sentences
- Present the breakpoint system as a table with breakpoint name, pixel value, column count, gutter, margin, and target devices
- Describe the layout at each breakpoint tier using structured text showing content block arrangement and dimensions
- Include CSS code snippets for the grid system, fluid typography, and key responsive patterns
- Provide a "Content Priority Matrix" table listing every content element with its visibility status at each breakpoint
- End with a "Responsive QA Checklist" covering the specific devices, orientations, and scenarios to test