What problem does it solve? Responsive interfaces often break at untested viewport sizes, causing horizontal scrolling, clipped overlays, and device-specific breakpoint debt. This Skill provides a rule set for building layouts that adapt cleanly across phones, foldables, laptops, and ultrawide desktops. ## Core Features & Use Cases - Breakpoint Strategy: Defines viewport tiers (Phone, Tablet, Desktop, Wide, XL) chosen by content design breaks rather than device names. - Container Query Guidance: Specifies component size classes (Compact, Standard, Expanded) so cards and modules adapt to their container, not just the viewport. - Anti-Pattern Detection: Flags common failures like body text touching viewport edges, edge-flush carousel cards, text overflow, and clipped dropdowns. - Use Case: When auditing a dashboard that breaks on mobile, apply the checklist to enforce minimum gutters, fluid grids, safe-area insets, and tap target sizing across the full test matrix. ## Quick Start Use the design-responsive-rules skill to audit this page layout and fix any horizontal scrolling or overflow issues across phone, tablet, and desktop widths.