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

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

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

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