responsive-and-adaptive-layout

name	responsive-and-adaptive-layout
description	Use when a browser-rendered page, component, dashboard, or email must adapt across widths using intrinsic layout, fluid values, breakpoints, or container queries. Do not use to establish the base grid or for fixed-canvas documents; route those to layout-grid-and-spacing.
metadata	{"portable":true,"category":"03-layout-grid-and-composition","compatible_with":["claude-code","codex"]}

Responsive And Adaptive Layout

Acknowledgement: Shared by Peter Bamuhigire, techguypeter.com.

Use When

• Building or restyling any browser-rendered artifact that must survive multiple widths: a website, landing page, web/app UI screen, dashboard, marketing email, or embeddable widget.
• Deciding breakpoints — how many, where, and whether they belong to the viewport or to a component's container.
• A component must adapt to wherever it is placed (a card in a 1-up hero vs the same card in a 4-up sidebar grid), not merely to the global window width — i.e. you need container queries.
• Deciding whether a value should be fixed, fluid, or intrinsic: column counts, gutters, type size, image sizing, and how they interpolate between sizes via clamp().
• An Apple-platform UI or web surface must survive iPhone resizability, iPad multitasking, Mac-designed-for-iPhone windows, iPhone Mirroring, Safari/WebKit viewport behavior, or intermediate window widths that are not named device breakpoints.
• A layout was designed desktop-first and "responsiveness" is being bolted on by stacking everything into one centred column on small screens — the slop tell this skill exists to remove.

Do Not Use When

• The page-level grid, spacing unit, focal point, and hierarchy are not yet decided — set those first in 03-layout-grid-and-composition/layout-grid-and-spacing, then make them respond here.
• The decision is purely which typeface (01-typography-and-fonts/font-selection-and-pairing) or purely which colours (02-color-brand-and-visual-identity). Set those, then size them here.
• The artifact is a fixed-canvas document or slide (DOCX/PPTX/PDF) with no fluid viewport — use layout-grid-and-spacing for page/slide grids; this skill targets resizable surfaces.
• The work is RTL mirroring or translation-expansion tolerance — that is internationalization-and-rtl-design (combine with it; logical properties below support both).
• Performance is the primary deliverable (budgets, CWV as a gate) — that is performance-as-ux-and-core-web-vitals. This skill respects those budgets; it does not own them.

Required Inputs

Input	Source	Required evidence
Realistic width and input-mode range	Product requirements, device support policy, or analytics	Minimum/maximum widths and keyboard, touch, or pointer needs
Base grid, hierarchy, and content priority	Layout skill and approved content model	Named focal point, grid tokens, and reflow priorities
Portable component inventory	Component library or interface audit	Placement contexts and widths at which each component fails
Performance and accessibility constraints	Project budgets and doctrine	CLS budget, zoom/text-resize target, and required platform states

• The target surfaces and their realistic width range (smallest phone to largest desktop/ultrawide the design must survive — not an assumed 320–1440 default).
• The content inventory and per-block importance from layout-grid-and-spacing (you re-compose hierarchy at each size; you cannot do that without knowing what should dominate).
• The chosen type scale and spacing unit from doctrine/references/type-scale-and-spacing.md (fluid type interpolates between scale steps; it does not invent new ones).
• Which components are context-portable (placed in more than one container width) — these are the container-query candidates, not viewport candidates.
• The performance budget from doctrine/references/web-performance-budgets-2026.md (CLS ≤ 0.1 in particular constrains how images and fluid blocks may resize).

Workflow

1. Start mobile-first, and design — don't reflow. Author the smallest realistic width first and let layout add structure as space appears (min-width media/container queries only). This is not just a CSS convention: it forces you to decide what the focal point and hierarchy are when space is scarcest, which is the honest test of a composition. Per layout-grid-and-spacing §8, each width is re-composed, never collapsed into one stacked column of identical cards — that collapse is the single most common responsive slop tell.

2. Prefer intrinsic, content-driven layout over breakpoints. Most "responsiveness" should need no breakpoint at all. Let CSS Grid and Flexbox respond to content and available space: grid-template-columns: repeat(auto-fit, minmax(min(100%, 16rem), 1fr)) reflows a card field from 1 to N columns with zero media queries and never produces a too-narrow column. Reach for an explicit breakpoint only where the design itself must change (a sidebar appears, a nav becomes a bar, the focal point moves) — not merely because the screen got wider. See references/container-queries-and-intrinsic.md.

3. Make portable components respond to their CONTAINER, not the viewport. A card, media object, or stat block that appears in several different column widths must adapt to where it is placed. Viewport media queries cannot do this — the same card is "wide" in a hero and "narrow" in a 4-up grid at the same viewport width. Use container queries: set container-type: inline-size on the wrapper and switch the component's internal layout with @container (min-width: …). This is the core modern capability of this skill — define the breakpoint where the component breaks, intrinsically, regardless of page context. Patterns in references/container-queries-and-intrinsic.md.

4. Choose breakpoints from the CONTENT, not from device names. Do not target "iPhone" or "iPad" widths. Resize until the layout breaks — a line gets too long (>~70–75ch), a column too narrow to hold its content, a focal point lost — and put a breakpoint there. Keep the set small (typically 2–4). Express widths in em/rem so breakpoints respect the user's font size. Full rationale and a starter scale in references/breakpoint-strategy.md.

5. Make size fluid with clamp() instead of stepping at breakpoints. Type, spacing, and measure should interpolate smoothly between a floor and a ceiling so the page bends rather than snapping. Fluid type: , where the floor and ceiling are real steps from (clamp interpolates the scale; it does not replace it). Always set a floor ceiling so text stays readable on tiny screens and never balloons on ultrawide, and so the user can still zoom (a pure- size defeats zoom — a WCAG 1.4.4 failure). Recipe in .

The Responsive Anti-Slop Checklist (run every time)

1. Mobile-first source order; each size re-composed, never collapsed into one identical-card stack.
2. Most reflow is intrinsic (Grid/Flex auto-fit/minmax/clamp) — breakpoints reserved for real design changes, and there are only a handful.
3. Portable components use container queries, not viewport queries, to adapt to their placement.
4. Breakpoints chosen where the content breaks, in em/rem — not at device-name pixel widths.
5. Fluid type via clamp() with a real rem floor and ceiling; zoom still works (no pure-vw).
6. Every image/media has reserved space (aspect-ratio/width+height); CLS ≤ 0.1 holds.
7. Logical properties (inline-size, margin-inline…) so RTL/vertical modes work; measure capped ~66ch.
8. A named focal point and at least one intentional asymmetry survive at the smallest size too.
9. prefers-reduced-motion, prefers-color-scheme, and coarse-pointer target sizes honoured.
10. Apple surfaces checked across resizable iPhone/iPad/Mac-designed-for-iPhone windows and Safari/WebKit viewport behavior where applicable.

Decision Rules

Condition	Choose	Wrong-choice failure
A component appears in differently sized parents	Container query at its content failure point	Viewport queries make the same component fail in sidebars or embeds
A value can interpolate safely	Bounded clamp() tied to approved scale endpoints	Abrupt jumps feel crude; unbounded fluid values become illegible
Structure changes because content no longer fits	Content-derived breakpoint	Device-name breakpoints leave damaging intermediate widths
Source order already matches reading/task order	CSS reflow without DOM duplication	Duplicate desktop/mobile markup creates accessibility and state drift
Dense information cannot remain useful when stacked	Recompose, prioritise, or provide controlled overflow	Blind one-column stacking destroys comparison and task context

Capability Contract

• Must inspect the source structure and render at representative and intermediate widths; may resize, measure overflow/CLS, and run accessibility checks.
• Review defaults to read-only. Change markup, styles, or tokens only for requested implementation/remediation, preserving semantic order and unrelated work.
• Do not claim device coverage from named breakpoints alone, or deploy/publish without separate authority and test evidence.

Degraded Mode

• If target widths or content priorities are unknown, stop structural breakpoint decisions and return a discovery matrix.
• If browser rendering is unavailable, provide intrinsic CSS and a viewport/container test plan marked unverified.
• If container queries are unsupported by a required environment, document the feature query and smallest maintainable fallback.
• Recover from overflow, overlap, CLS, or order failure by fixing the earliest governing rule, then retest boundary widths on both sides of it.

Quality Standards

• No horizontal overflow, clipped critical content, hidden action, or semantic-order mismatch at tested boundary and intermediate widths.
• Zoom, text resizing, touch/pointer input, reduced motion, and representative content remain usable where applicable.
• Release evidence names browsers, widths, containers, states, failures, corrections, and residual compatibility risks.

Anti-Patterns

• The desktop mockup with mobile bolted on: designed at 1440 only, then everything stacks into one centred column of identical cards on phones — hierarchy and focal point destroyed.
• Device-width breakpoints: @media (max-width: 768px) chasing yesterday's iPad instead of putting the breakpoint where this content actually breaks.
• Viewport queries for component-level adaptivity: forcing a card to know the window width when it should respond to its own container; the card then looks wrong in any non-default placement.
• Breakpoint soup: a dozen max-width queries hand-tuning every element because the base layout isn't intrinsic; brittle, and it snaps instead of bending.
• Pure-vw font sizing: font-size: 5vw with no floor/ceiling — illegible on small screens, gigantic on ultrawide, and it breaks browser zoom (WCAG 1.4.4 reflow/zoom failure).
• Unreserved media: images with no width/height/aspect-ratio that shove content down as they load — a visible CLS jump and an instant "unconsidered" read.
• Max-width-only (desktop-first) cascades: authoring large then subtracting, which buries the scarcest-space decision instead of confronting it first.
• Ignoring the person: no reduced-motion, no dark-scheme, desktop-sized hit targets on touch.

Sourcing authority (the asymmetry rule)

Grounds only in human design and web-standards authority — never in an AI tool's responsive suggestions, per doctrine/design-doctrine.md §2. Canonical sources for this skill:

• Ethan Marcotte — Responsive Web Design — fluid grids, flexible media, media queries as a single adaptable layout rather than per-device mockups.
• Jeremy Keith — Resilient Web Design and progressive enhancement — build up from the smallest, most robust layer outward.
• Andy Bell & Heydon Pickering — Every Layout — intrinsic, algorithmic layouts that respond to content and space with minimal media queries.
• The CSS specifications (CSS Grid, Containment / Container Queries, clamp() math functions, logical properties) as the standards basis — admissible as standards, not as AI endorsement.
• Builds directly on 03-layout-grid-and-composition/layout-grid-and-spacing (the grid, spacing unit, focal point, and asymmetry this skill makes responsive).

When an AI tool recommends "three max-width breakpoints at 768/1024/1280 with everything stacking on mobile," treat that as the convergent mean to avoid — not as endorsement.

Outputs

Output	Consumer	Evidence and acceptance
Responsive behaviour specification	Designer and frontend implementer	Intrinsic rules, breakpoints, container queries, fluid ranges, and priority changes are explicit
Boundary test matrix	QA and accessibility reviewer	Representative widths/containers and critical states pass without overflow or order defects
Release gate record	Approver	Render evidence, performance/accessibility checks, fallbacks, and unresolved risks are recorded

• A stated responsive decision before any markup/CSS: the breakpoint set (and the content reason for each), which components are container-query-driven, the fluid-type clamp() floors and ceilings (tied to the type scale), and how the focal point + asymmetry re-compose at each size — including the smallest.
• The responsive CSS itself (intrinsic grid, container queries, fluid type/space) — see examples/responsive-grid-template.md.
• A completed responsive anti-slop checklist, consistent with the Mission in doctrine/design-doctrine.md §0 and within the budgets of doctrine/references/web-performance-budgets-2026.md.

Examples

• examples/responsive-grid-template.md — a complete, real responsive card grid: intrinsic auto-fit/minmax reflow, a container-query-driven card that changes its own internal layout by available width, and fluid type/space via clamp() — annotated against the checklist.

References

• doctrine/design-doctrine.md (§0 Mission — "the moat is looking human-made"; §2 sourcing- authority asymmetry rule).
• doctrine/references/type-scale-and-spacing.md (the scale steps and spacing unit that fluid clamp() interpolates between — clamp does not invent sizes).
• doctrine/references/web-performance-budgets-2026.md (CLS ≤ 0.1, responsive image budgets, font-display/preload — the constraints fluid sizing and media must respect).
• doctrine/references/wcag-2.2-criteria.md (1.4.4 zoom/reflow for fluid type; 2.5.8 target size for coarse-pointer adaptivity).
• 03-layout-grid-and-composition/layout-grid-and-spacing (the grid, spacing unit, focal point, and intentional asymmetry this skill carries responsively across sizes).
• references/container-queries-and-intrinsic.md and references/breakpoint-strategy.md.