PostHog · DESIGN.md

Overview

PostHog's marketing system is built on the visual contradiction at the heart of the brand: a serious open-source product analytics platform rendered as if it were a friendly engineering sketchbook. The chrome runs on a warm cream canvas ({colors.canvas} — #eeefe9) — not white — and every page is dotted with hand-drawn hedgehog mascots in lab coats, lounge chairs, terminals, and reading glasses, scattered across the layout like marginalia in a textbook. Type sits in IBM Plex Sans Variable at olive-gray ({colors.body} — #4d4f46) for body and deep olive-charcoal ({colors.ink} — #23251d) for headlines, with weights stepped tightly between 400, 600, 700, and 800 to create hierarchy without color. The single saturated yellow-orange pill ({colors.primary} — #f7a501) is the brand's only loud chromatic moment; everything else is cream, olive, white card, and the occasional pastel callout band.

The system has a distinctive two-mode body layout: marketing pages (home, workflows, pricing) lean on alternating-pastel callout bands and feature tiles in white cards on cream, while documentation pages add a sticky 240px left sidebar with a rounded outline-icon section list. Code samples are full-width dark blocks on {colors.surface-dark} (the same olive-charcoal that carries body ink, used inverted) inside white doc cards, creating the system's most distinctive visual moment: a dark-on-dark code island floating inside a white card on a cream canvas, with a hedgehog mascot doodled in the margin.

Sections stack at {spacing.section} (80px) rhythm with cream canvas continuing edge-to-edge between them. The only color bands that interrupt the cream are pastel {component.banner-tip-blue} / -green / -red / -purple callout panels inside doc articles — soft tinted boxes that carry "💡 Tip", "✅ Success", "⚠️ Warning", "📘 Info" inline annotations. There are no decorative gradients, no atmospheric mesh backgrounds, and no full-bleed dark hero chapters; the cream canvas runs uninterrupted top to bottom and the hedgehogs are the entire visual identity.

Key Characteristics:

Warm cream canvas ({colors.canvas} — #eeefe9) end-to-end with no surface alternation between sections — the page is one continuous sheet
Single yellow-orange CTA pill ({colors.primary} — #f7a501) with deep olive text ({colors.on-primary}) — the brand's only saturated color
IBM Plex Sans Variable across every text role with weights 400/500/600/700/800 — no other typeface in the system
Hand-drawn hedgehog mascots scattered across the layout as the entire decorative system — no gradients, no mesh, no atmospheric backgrounds
4–8px radius card vocabulary: {rounded.md} (6px) for most components, {rounded.lg} (8px) for select containers, fully rounded for pill chips
Pastel callout banners ({colors.accent-blue-soft}, {colors.accent-green-soft}, {colors.accent-red-soft}, {colors.accent-purple-soft}) break up doc article body with soft tinted side rails for tips/warnings/info
Documentation pages add a sticky 240px {component.doc-sidebar} with rounded outline-icon section nav and an "Ask PostHog AI" CTA at the top

Colors

Source pages: / (home), /pricing (pricing detail), /docs/product-analytics (docs article), /workflows (product feature page). The chrome palette is identical across all four pages — only doc-specific accents (callout-banner pastels, code-block dark surface) appear exclusively inside the docs experience.

Brand & Accent

PostHog Yellow ({colors.primary} — #f7a501): the universal primary CTA. Sticky "Get started — free" pill in the top-right of every nav, hero CTAs, pricing-tier subscribe buttons, footer signup pill. The system's only saturated chromatic moment.
Yellow Pressed ({colors.primary-pressed} — #dd9001): pressed state for the primary pill.
Yellow Active ({colors.primary-active} — #b17816): deeply-pressed yellow + the system's gold-toned border accent (rare 1px gold rule on inline form elements).

Surface

Canvas ({colors.canvas} — #eeefe9): the warm cream page background. End-to-end on every page; the brand's most distinctive surface choice.
Soft Surface ({colors.surface-soft} — #e5e7e0): button-secondary fill, sub-nav strip background, inline-code chip background.
Surface Card ({colors.surface-card} — #ffffff): true white card and tile background sitting on top of the cream canvas. The dominant card surface.
Surface Doc ({colors.surface-doc} — #fcfcfa): a faintly cream-warm white used inside doc article body cards — slightly softer than pure white to keep the page tonally unified.
Surface Dark ({colors.surface-dark} — #23251d): the deep olive-charcoal used inverted as code-block background. The same hex as {colors.ink} — the brand uses one olive-near-black for both text and dark code surfaces.
Hairline ({colors.hairline} — #bfc1b7): 1px card border, table rule, footer column dividers.
Hairline Soft ({colors.hairline-soft} — #dcdfd2): in-card row divider, soft inset rule.
On Dark ({colors.on-dark} — #ffffff): primary text on {colors.surface-dark} code blocks.

Text

Ink ({colors.ink} — #23251d): headlines, button text on light, primary nav links — deep olive-charcoal that reads near-black against cream.
Body ({colors.body} — #4d4f46): default paragraph text, doc article body, inline link color before hover. The brand's most-used text color.
Charcoal ({colors.charcoal} — #33342d): emphasized body text where body is too soft.
Mute ({colors.mute} — #6c6e63): metadata, footer link text, in-list secondary annotations.
Ash ({colors.ash} — #9b9c92): disabled-state text and lowest-emphasis utility.
Stone ({colors.stone} — #b6b7af): least-emphasis caption text and disabled icon color.

Semantic

Link Blue ({colors.link-blue} — #1d4ed8): inline anchor link inside body prose. The system's primary informational link color.
Link Teal ({colors.link-teal} — #1078a3): doc-article inline link variant, paired with body text.
Accent Blue ({colors.accent-blue} — #2c84e0) + Accent Blue Soft ({colors.accent-blue-soft} — #dceaf6): "💡 Tip / Info" callout banner inside docs.
Accent Red ({colors.accent-red} — #cd4239) + Accent Red Soft ({colors.accent-red-soft} — #f7d6d3): "⚠️ Warning / Caution" callout banner.
Accent Green ({colors.accent-green} — #2c8c66) + Accent Green Soft ({colors.accent-green-soft} — #d9eddf): "✅ Success / Positive" callout banner.
Accent Purple ({colors.accent-purple} — #7c44a6) + Accent Purple Soft ({colors.accent-purple-soft} — #e7d8ee): "📘 Note / Reference" callout banner.
Focus Ring ({colors.focus-ring} — rgba(59,130,246,0.5)): translucent blue browser-default focus ring around interactive elements.

Typography

Font Family

IBM Plex Sans Variable is the system's primary face — used across every text role on every page at weights 400 (regular), 500 (medium), 600 (semibold), 700 (bold), and 800 (extra-bold). Falls back through IBM Plex Sans → -apple-system → system-ui → broad cross-platform sans stack.

ui-monospace + Source Code Pro carry code samples and inline-code chips at 14px / 1.43 line-height. Source Code Pro is the explicit display monospace; ui-monospace handles inline <code> chips.

The brand-distinctive choice is the mixed weight ladder (400 / 500 / 600 / 700 / 800) — most chrome lives in the 400–700 band, with weight 800 reserved exclusively for the larger display headlines on home and pricing. This gives the system its "engineering blog" feel: hierarchy is built from weight contrast much more than from size.

Hierarchy

Token	Size	Weight	Line Height	Letter Spacing	Use
`{typography.display-xl}`	36px	700	1.5	0	Hero headline ("The new way to build products")
`{typography.display-lg}`	24px	800	1.33	-0.6px	Section headline, pricing tier name
`{typography.heading-lg}`	21px	700	1.4	-0.5px	Sub-section heading, doc-article H2
`{typography.heading-md}`	20px	700	1.4	0	Card group title, in-grid heading
`{typography.heading-sm}`	18px	700	1.5	0 (uppercase)	Section eyebrow ("UNDERSTAND PRODUCT USAGE")
`{typography.heading-sm-mixed}`	18px	600	1.56	0	Card title in mixed-case (no uppercase transform)
`{typography.body-md}`	16px	400	1.5	0	Body copy, default paragraph
`{typography.body-strong}`	16px	600	1.5	0	Inline emphasis, primary nav link, in-card label
`{typography.body-sm}`	15px	400	1.71	0	Doc article body, marketing card description
`{typography.body-sm-strong}`	15px	600	1.71	0	Sub-section emphasis inside doc article
`{typography.body-xs}`	14px	500	1.43	0	Doc sidebar item, metadata, in-list caption
`{typography.caption-md}`	14px	700	1.71	0	Card eyebrow, link cluster header
`{typography.caption-sm}`	13px	500	1.5	0	Compact metadata caption
`{typography.caption-xs}`	12px	600	1.33	0 (uppercase)	Inline badge label
`{typography.utility-xs}`	12px	700	1.33	0 (uppercase)	Section-eyebrow utility text, footer category header
`{typography.link-md}`	16px	400	1.5	0	Inline body anchor link
`{typography.button-md}`	14px	700	1.5	0	Standard primary/secondary button label
`{typography.button-sm}`	13px	500	1	0	Pill chip / compact CTA
`{typography.code-sm}`	14px	400	1.43	0	Code block content
`{typography.code-xs}`	14px	500	1.43	0	Inline code chip

Principles

The hierarchy is explicitly built from weight + size + occasional uppercase transform — there is no italic style, no decorative display variant, no proprietary face. The biggest display moments use weight 800 with -0.6px tracking, and the body settles at 400 with 1.5 line-height; everything else fills the band between. Section eyebrows ({typography.heading-sm} and {typography.utility-xs}) consistently render uppercase, which gives the doc layout its textbook-chapter feel.

Note on Font Substitutes

IBM Plex Sans Variable is open-source and Google-Fonts-hosted. There is no need for a substitute — load it directly. If a substitute is genuinely needed, Inter is the closest geometric match at all five weights; pair with Inter's letter-spacing -0.5 to -0.6px on display sizes to approximate Plex's display tracking. For monospace, JetBrains Mono is a near-perfect substitute for Source Code Pro at body sizes.

Layout

Spacing System

Base unit: 8px (with finer 2/4/6px steps for tight inline gaps in callout banners and pill buttons).
Tokens (front matter): {spacing.xxs} (2px) · {spacing.xs} (4px) · {spacing.sm} (8px) · {spacing.md} (12px) · {spacing.lg} (16px) · {spacing.xl} (24px) · {spacing.xxl} (32px) · {spacing.section} (80px).
Universal section rhythm: every page in the set uses {spacing.section} (80px) as the vertical gap between major content blocks. Card grids use {spacing.lg} (16px) gutters; card internal padding sits at {spacing.xl} (24px) for product cards and {spacing.xxl} (32px) for pricing tier cards.

Grid & Container

Max width: ~1280px content area at desktop with 24px gutters (~48px at ultrawide). Doc article body sits at ~720px max width with the 240px sidebar pushing the article column right of center.
Marketing card grid: 4-up at desktop, 3-up at 1024px, 2-up at 768px, 1-up at 480px. Cards preserve a fixed 1:1 or 4:3 ratio.
Pricing tier grid: 3-up at desktop with a left rail of plan info, collapsing to 2-up + 1 at tablet and 1-up at mobile.
Doc layout: desktop 240px sticky left sidebar + ~720px article body + (optional) 200px right TOC rail = ~1160px content width.
Footer: 6-column horizontal link grid at desktop, 3-up at tablet, 2-up at mobile.

Whitespace Philosophy

Whitespace is generous on marketing pages and tight on doc pages. The home and workflows pages stack feature tiles with {spacing.lg} (16px) gutters and 24px internal padding, while doc articles tighten internal spacing to {spacing.md} (12px) between paragraphs to maximize information density. The cream canvas runs continuously through every section — there are no decorative dividers, no shaded section bands; only the 1px hairline beneath section eyebrows and footer column rules separate content blocks.

Elevation & Depth

Level	Treatment	Use
0 — Flat	No border, no shadow	Default for canvas-on-canvas blocks, hero text, body sections
1 — Hairline border	1px solid `{colors.hairline}`	Marketing cards, pricing tier cards, doc sidebar items, footer column rules
2 — Hairline soft	1px solid `{colors.hairline-soft}`	In-card row divider between adjacent rows
3 — Inverted dark code block	`{colors.surface-dark}` fill	Code samples inside doc cards — the system's only "elevated" surface uses color, not shadow

The system has no drop-shadow elevation in marketing or product chrome. Cards sit flat on cream with thin olive borders. The single inverted moment is the dark code-block surface used inside doc article body cards.

Decorative Depth

Depth comes entirely from illustration and the pastel callout band system, not from CSS effects:

Hand-drawn hedgehog mascots — characters in various costumes (lab coat, terminal, lounge chair, magnifying glass, hammock, hat) scattered across pages as marginalia. Always rendered as flat color illustrations, never photographs.
Pastel callout banners — {component.banner-tip-blue} / -green / -red / -purple soft tinted side-rail panels inside doc articles, each prefixed with an emoji icon (💡 ✅ ⚠️ 📘) and carrying tip/warning/note copy.
Code blocks — full-width dark olive-charcoal panels on {colors.surface-dark} with white code text. The system's most cinematic surface, used inside white doc cards.
Outline product icons in the doc sidebar — small rounded-square mini-illustrations (chart icon, funnel, session-replay icon) mark each major product section.

Shapes

Border Radius Scale

Token	Value	Use
`{rounded.none}`	0px	Sub-nav strip, footer, doc sidebar, primary nav — flat structural surfaces
`{rounded.xs}`	2px	Inline `<code>` chips, micro-rule highlights
`{rounded.sm}`	4px	Inline buttons, form inputs, micro chips
`{rounded.md}`	6px	Marketing cards, pricing cards, doc cards, code blocks, every standard CTA
`{rounded.lg}`	8px	Tab top corners (`6px 6px 0 0` on active tab) and rare large containers
`{rounded.full}`	9999px	Pill chips and pill-style CTAs ("Get started — free" sticky CTA in nav)

The radius vocabulary clusters around 4–6px for nearly everything; the only fully-rounded element is the pill-style sticky nav CTA and inline pill chips.

Photography Geometry

There is no photography. Visual elements are limited to:

Hedgehog character illustrations — flat-color cartoon hedgehogs ranging from ~80px (in-card mascot) to ~240px (hero illustration). Always at native aspect, never cropped to a frame.
Outline product icons in the doc sidebar — 20–24px rounded-square illustrations.
Inline emoji at 14–16px inside callout banners (💡 ✅ ⚠️ 📘) — used as functional iconography rather than decoration.
Section illustrations on the home page — small hedgehog vignettes paired with each "Understand product usage" / "Build sticky habits" / "Test before launch" feature row.

Components

No hover states documented per system policy. Each spec covers Default and Active/Pressed only.

Buttons

button-primary — the universal PostHog CTA

Background {colors.primary} (yellow-orange), text {colors.on-primary} (deep olive), type {typography.button-md}, padding 8px 16px, height 40px, rounded {rounded.md}.
Used for "Get started — free" (sticky top-nav CTA), "Sign up", "Try it free", "Subscribe" — every primary action.
Pressed state lives in button-primary-pressed — background drops to {colors.primary-pressed}.

button-secondary — soft alternative on cream canvas

Background {colors.surface-soft} (#e5e7e0), text {colors.ink}, type {typography.button-md}, padding 8px 16px, height 40px, rounded {rounded.md}.
"Talk to sales", "Read docs", "Watch demo" — second-tier actions paired with the yellow primary.

button-tertiary — ghost text button

Background transparent, text {colors.ink}, type {typography.button-md}, padding 8px 12px, rounded {rounded.md}.
Lowest-emphasis action: "See all docs →", "Browse all features".

button-disabled

Background {colors.surface-soft}, text {colors.ash} — flat soft cream-gray.

Tabs & Chips

product-tab + product-tab-active — major product section tabs

Default: transparent background, text {colors.body}, type {typography.body-strong}, padding 8px 12px, rounded {rounded.md}.
Active: background flips to {colors.surface-card} (white), text {colors.ink} — the tab card lifts off the cream canvas as the visual signal of selection.

pill-tab + pill-tab-active — compact filter pill

Default: transparent background, text {colors.body}, type {typography.button-sm}, padding 6px 14px, rounded {rounded.full}.
Active: background flips to {colors.ink}, text {colors.on-dark} — the chip flips fully inverted on selection.

badge-uppercase — text-only utility label

Background transparent, text {colors.body} in {typography.utility-xs} (uppercase) — used as in-list category prefix ("FEATURE FLAG", "EXPERIMENT", "HEATMAP").

badge-promo — small inline pill chip

Background {colors.accent-blue-soft}, text {colors.link-blue}, type {typography.caption-xs}, padding 2px 8px, rounded {rounded.full}.
"New", "Beta", "Coming soon" pill labels overlaid on cards.

Inputs & Forms

text-input + text-input-focused

Default: background {colors.surface-card}, text {colors.ink}, 1px solid {colors.hairline}, type {typography.body-md}, padding 8px 12px, height 36px, rounded {rounded.md}.
Focused: same surface; 2px solid {colors.accent-blue} border replaces the 1px hairline + a translucent {colors.focus-ring} outline.

search-input — utility search field (doc sidebar, "Ask PostHog AI")

Same dimensions as text-input with a magnifier glyph at the left edge in {colors.mute}.

Cards & Containers

product-card — marketing tile / feature card

Container: background {colors.surface-card} (white), 1px solid {colors.hairline}, padding {spacing.xl} (24px), rounded {rounded.md}.
Layout: small hedgehog illustration at top-left, {typography.heading-sm-mixed} title, {typography.body-sm} description, optional {component.button-tertiary} "Learn more →" link.

doc-card — doc article body card

Container: background {colors.surface-doc} (#fcfcfa warm-white), 1px solid {colors.hairline}, padding {spacing.xl} (24px), rounded {rounded.md}.
Carries article body sections, code blocks, callout banners, and tables inside doc pages.

feature-tile — small marketing feature tile

Container: background {colors.surface-card}, 1px solid {colors.hairline}, padding {spacing.lg} (20px), rounded {rounded.md}.
Used in 3-up or 4-up grids on home and workflows pages — paired with a small icon and a 1-line description.

pricing-tier-card — pricing plan card

Container: background {colors.surface-card}, 1px solid {colors.hairline}, padding {spacing.xxl} (32px), rounded {rounded.md}.
Layout: tier name in {typography.display-lg} (24px / 800 / -0.6px), large price + period, feature checklist with check-icon bullets, primary or secondary CTA at bottom.

hedgehog-mascot-card — feature card with margin-anchored hedgehog

Same chrome as {component.product-card} but with a hand-drawn hedgehog illustration anchored in the right margin or top-right corner — the brand's signature card variant.

Callout Banners

banner-tip-blue + banner-tip-green + banner-tip-red + banner-tip-purple

Background {colors.accent-blue-soft} / {colors.accent-green-soft} / {colors.accent-red-soft} / {colors.accent-purple-soft}, text {colors.ink}, type {typography.body-md}, padding 16px 20px, rounded {rounded.md}.
Each prefixed with an inline emoji icon (💡 / ✅ / ⚠️ / 📘) followed by an inline label and body copy.
Only appear inside doc article body. The four-color callout family is the brand's information-architecture vocabulary for inline tips/warnings/info inside long-form documentation.

Code

code-block — dark code sample inside doc card

Container: background {colors.surface-dark} (deep olive-charcoal), text {colors.on-dark} in {typography.code-sm}, padding 16px 20px, rounded {rounded.md}.
Syntax highlighting uses muted accent colors (blue for keywords, green for strings, purple for numbers) — never the bright accent colors used in callout banners.

inline-code — small inline <code> chip

Background {colors.surface-soft}, text {colors.ink} in {typography.code-xs}, padding 2px 6px, rounded {rounded.xs} (2px).
Used inside body prose to mark code snippets and identifiers.

Navigation

primary-nav

Background {colors.canvas} (cream — same as the page), text {colors.ink}, height 56px, type {typography.body-strong}, rounded {rounded.none}.
Layout (desktop): PostHog wordmark + hedgehog logo at left, nav menu cluster ("Pricing · Docs · Community · Company"), right cluster with a search-glyph, "Login" link, and the always-yellow {component.button-primary} "Get started — free" pill anchored to the far right.

sub-nav-strip — secondary nav bar (under primary)

Background {colors.surface-soft}, text {colors.body} in {typography.body-xs}, height 40px, rounded {rounded.none}.
Sits directly below the primary nav on workflows / product pages with section anchor links and a contextual "Get started →" link at the right.

doc-sidebar — sticky doc-page left sidebar

Background {colors.canvas}, text {colors.body} in {typography.body-xs}, width 240px, rounded {rounded.none}.
Layout: search-input "Ask PostHog AI" at top, then a vertical list of section headers each with a small rounded outline-icon mini-illustration, then nested item links indented under the active header.

Top Nav (Mobile)

Hamburger menu icon at left, PostHog wordmark + hedgehog at center, search + sticky yellow "Get started — free" CTA at right. Primary nav collapses into a full-height drawer that slides from the left.

Footer

footer-section

Background {colors.canvas}, text {colors.body} in {typography.body-xs}, padding 32px 24px, rounded {rounded.none}, with a 1px {colors.hairline} top rule.
Layout: 6-column horizontal link grid (Product · Resources · Company · Community · Pricing · Legal), each column with a {typography.utility-xs} (uppercase) header and a vertical list of links in {typography.body-xs} {colors.body}.
Bottom row: PostHog wordmark + small hedgehog illustration, copyright in {typography.caption-xs} {colors.mute}, social-icon row at far-right.

Inline

link-inline — body-prose anchor link

{colors.link-teal} (#1078a3) in body prose with no underline by default; underline appears on focus. The brand's primary inline link color.

Do's and Don'ts

Do

Use {colors.canvas} (cream — #eeefe9) as the page body. Never substitute pure white as the canvas.
Reserve {colors.primary} (yellow-orange) for the primary CTA pill only. The "Get started — free" treatment is the brand's anchor.
Render the brand wordmark with the hedgehog illustration alongside it, not as a stand-alone wordmark. The hedgehog IS the brand identity.
Use IBM Plex Sans Variable across every text role — body 400, emphasis 600/700, display 800.
Stack content sections at {spacing.section} (80px) rhythm with no decorative dividers between them; let the cream canvas continue uninterrupted.
Use {component.banner-tip-blue} / -green / -red / -purple only inside doc article body for tip/warning/note panels — keep marketing chrome out of the four-color callout family.
Pair every code sample with the dark {component.code-block} surface; inline <code> chips use {component.inline-code} (cream surface-soft chip).
Anchor a hedgehog mascot illustration in feature tile margins on home and workflows pages — the system's signature decoration.

Don't

Don't introduce drop shadows on cards. Cards sit flat on cream with thin olive borders only.
Don't add a second saturated chromatic CTA. Yellow-orange is the only loud color in the system.
Don't replace the cream canvas with pure white or full-bleed dark hero bands. The cream is the brand.
Don't use the four-color callout banner pastels ({colors.accent-blue-soft}, -green, -red, -purple) as marketing-card backgrounds. They belong to inline doc content only.
Don't substitute the hedgehog illustration with a generic icon set. The character system is the brand.
Don't use uppercase transform outside of {typography.heading-sm}, {typography.utility-xs}, and {typography.caption-xs}. Uppercase is reserved for eyebrows and footer category headers.
Don't pad cards with 32px+ on all sides except for {component.pricing-tier-card}. Standard cards sit at 24px internal padding.

Responsive Behavior

Breakpoints

Name	Width	Key Changes
ultrawide	1920px+	Content max-width holds at 1280px; outer gutters grow to ~80px
desktop-large	1440px	Default — 4-up feature tile grid, 240px sticky doc sidebar visible
desktop	1280px	Same layout with narrower outer gutters
desktop-small	1024px	4-up tiles collapse to 3-up; doc sidebar remains visible
tablet	768px	3-up tiles collapse to 2-up; doc sidebar collapses into a top accordion; primary nav becomes hamburger
mobile	480px	Single-column everything; hero `{typography.display-xl}` scales 36px → ~28px
mobile-narrow	320px	Section padding tightens to 32px

Touch Targets

All interactive elements meet WCAG AA (≥ 40×40px). {component.button-primary} and {component.button-secondary} sit at 40px height with 16px padding. {component.text-input} sits at 36px (just under AAA but above AA at this size). {component.pill-tab} is ~32–36px height with 14px padding extending to ~44px tappable via inline padding. Doc-sidebar items use 14px text with ~32px line-height + 6px vertical padding for ~44px tap rows.

Collapsing Strategy

Primary nav: desktop horizontal cluster → tablet hamburger drawer at 768px. The yellow "Get started — free" CTA stays visible at every breakpoint.
Sub-nav strip: desktop horizontal anchor row → tablet horizontal scroll → mobile select dropdown.
Marketing card grid: 4-up → 3-up → 2-up → 1-up at 1024, 768, and 480px; gutters drop from 16px to 12px on mobile.
Pricing grid: 3-up → 2+1 → 1-up stacked at tablet and below.
Doc layout: desktop 240px sidebar + 720px article → tablet sidebar collapses to a top accordion → mobile fully collapsed accordion.
Footer: 6-up link columns → 3-up at tablet → 2-up at mobile.
Section padding: {spacing.section} (80px) desktop → 64px tablet → 48px mobile.
Hero headline: {typography.display-xl} (36px) at desktop, scaling to ~28px at mobile, line-height holding at 1.5.

Image Behavior

The only "imagery" in the system is hand-drawn hedgehog illustrations rendered as inline SVG. They preserve their natural aspect at every breakpoint and scale via CSS width: auto; max-width: 100%. There is no responsive art-direction needed because there is no photography.

Iteration Guide

Focus on ONE component at a time. Pull its YAML entry and verify every property resolves.
Reference component names and tokens directly ({colors.primary}, {component.button-primary-pressed}, {rounded.md}) — do not paraphrase.
Run npx @google/design.md lint DESIGN.md after edits — broken-ref, contrast-ratio, and orphaned-tokens warnings flag issues automatically.
Add new variants as separate component entries (-pressed, -disabled, -focused) — do not bury them inside prose.
Default body to {typography.body-md} (16px / 400 / 1.5); reach for {typography.body-strong} for emphasis; reserve {typography.display-lg} (24px / 800) strictly for marketing display moments.
Keep {colors.primary} scarce per viewport — at most one yellow-orange pill per fold.
When introducing a new component, ask whether it can be expressed with the existing card + 6px-radius + cream-canvas vocabulary before adding new tokens. The system's strength is that it almost never needs new ones.

Known Gaps

Mobile screenshots not captured — responsive behavior synthesizes PostHog's mobile pattern (hamburger drawer, single-column grid, doc sidebar accordion) from desktop evidence and the breakpoint stack.
Hover states not documented by system policy.
In-product app chrome (PostHog dashboard, charts, session replay player) not in the captured set — the marketing site is documented here, not the in-product analytics interface.
Authenticated chrome (login modal, account dashboard, billing settings) not in the captured pages.
Form validation states beyond the focused-state input not present in the captured surfaces.
Marketing illustration set — the full library of hedgehog character poses is not enumerated here; specific poses (lab coat hedgehog, terminal hedgehog, hammock hedgehog) are noted as visible in screenshots but the full asset library is page-specific.