Posthog UI Skills

Opinionated constraints for building Posthog-style interfaces with AI agents.

When to Apply

Reference these guidelines when:

• Building dark-mode interfaces

• Creating Posthog-inspired design systems

• Implementing UIs with Inter font and 4px grid

Colors

• MUST use dark backgrounds (lightness < 20) for primary surfaces - detected lightness: 0

• MUST use #000000 as page background (surface-base )

• SHOULD limit color palette to 5 distinct colors

• MUST maintain text contrast ratio of at least 4.5:1 for accessibility

Semantic Tokens

Token HEX RGB Usage

surface-base

#000000 rgb(0,0,0) Page background

surface-raised

#E38B20 rgb(227,139,32) Cards, modals, raised surfaces

text-primary

#52290C rgb(82,41,12) Headings, body text

text-secondary

#55554A rgb(85,85,74) Secondary, muted text

border-default

#C17C25 rgb(193,124,37) Subtle borders, dividers

destructive

#52290C rgb(82,41,12) Error states, delete actions

warning

#C17C25 rgb(193,124,37) Warning states, cautions

Typography

• MUST use Inter as primary font family

• SHOULD use single font family for consistency

• MUST use 14px / 400 for primary headings

• MUST limit font weights to: regular, light

• MUST use text-balance for headings and text-pretty for body text

• SHOULD use tabular-nums for numeric data

• NEVER modify letter-spacing unless explicitly requested

Text Styles

Style Font Size Weight Color Count

heading-1

Inter 14px 400 #626257 1

heading-2

Inter 13px 300 #545449 1

heading-3

Inter 12px 400 #5B5B50 1

caption

Inter 11px 400 #58584D 1

label

Inter 10px 400 #52290C 1

label

Inter 10px 400 #55554A 1

label

Inter 10px 400 #56564B 1

Typography Reference

Font Families:

• Inter (used 7x)

Font Sizes: 10px, 11px, 12px, 13px, 14px

Spacing

• MUST use 4px grid for spacing

• SHOULD use spacing from scale: 3px, 4px, 9px, 10px

• SHOULD use 4px as default gap between elements

• NEVER use arbitrary spacing values (use design scale)

• SHOULD maintain consistent padding within containers

Borders

• MUST use border-radius from scale: 3px

• MUST use 1px border width consistently

• SHOULD use 3px as default border-radius

• NEVER use arbitrary border-radius values (use design scale)

• SHOULD use subtle borders (1px) for element separation

Border Radius Reference

Scale: 3px

Layout

• MUST design for 1920px base viewport width

• SHOULD use consistent element widths: 41px, 24px, 43px, 857px, 12px

• NEVER use h-screen , use h-dvh for full viewport height

• MUST respect safe-area-inset for fixed elements

• SHOULD use size-* for square elements instead of w-*

• h-*

Detected Layout Patterns

• Header: height: 39px

• Main Content: width: 1920px, height: 1050px

• Main Content: width: 1920px, height: 1043px

Components

Buttons

Variant Background Text Border Height Radius

Ghost transparent #52290C none

Interactive States

Focus

• MUST use 2px outline with accent color (#5E6AD2 )

• MUST use 2px outline-offset

• NEVER remove focus indicators

Hover

• Buttons (primary): lighten background by 10%

• Buttons (secondary): use #E38B20 background

• List items: use #E38B20 background

Disabled

• MUST use opacity: 0.5

• MUST use cursor: not-allowed

Interaction

• MUST use an AlertDialog for destructive or irreversible actions

• SHOULD use structural skeletons for loading states

• MUST show errors next to where the action happens

• NEVER block paste in input or textarea elements

• MUST add an aria-label to icon-only buttons

Animation

• NEVER add animation unless it is explicitly requested

• MUST animate only compositor props (transform , opacity )

• NEVER animate layout properties (width , height , top , left , margin , padding )

• SHOULD use ease-out on entrance animations

• NEVER exceed 200ms for interaction feedback

• SHOULD respect prefers-reduced-motion

Performance

• NEVER animate large blur() or backdrop-filter surfaces

• NEVER apply will-change outside an active animation

• NEVER use useEffect for anything that can be expressed as render logic