Mobbin UI Skills

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

When to Apply

Reference these guidelines when:

• Building light-mode interfaces

• Creating Mobbin-inspired design systems

• Implementing UIs with Inter font and 4px grid

Colors

• SHOULD use light backgrounds for primary surfaces

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

• SHOULD reduce color palette (currently 11 colors detected)

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

Semantic Tokens

Token HEX RGB Usage

surface-base

#FFFFFF rgb(255,255,255) Page background

surface-raised

#0F0F0F rgb(15,15,15) Cards, modals, raised surfaces

surface-overlay

#EEEEEF rgb(238,238,239) Overlays, tooltips, dropdowns

text-primary

#B1B1B1 rgb(177,177,177) Headings, body text

text-secondary

#939393 rgb(147,147,147) Secondary, muted text

text-tertiary

#4A4A4A rgb(74,74,74) Additional text

border-default

#DEDEDE rgb(222,222,222) Subtle borders, dividers

Typography

• MUST use Inter as primary font family

• SHOULD use single font family for consistency

• MUST use 75px / 700 for primary headings

• MUST use 18px / 400 for body text

• MUST limit font weights to: bold, regular, medium

• 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 75px 700 #1B1B1B 1

text-20px

Inter 20px 500 #ACACAC 1

text-19px

Inter 19px 400 #7C7C7C 1

body

Inter 18px 400 #B3B3B3 1

body-secondary

Inter 18px 500 #3A3A3A 1

body-secondary

Inter 16px 500 #AFAFAF 2

body-secondary

Inter 16px 500 #B2B2B2 1

body-secondary

Inter 16px 500 #B5B5B5 1

body-secondary

Inter 15px 400 #4D4D4D 2

body-secondary

Inter 15px 500 #B1B1B1 1

Typography Reference

Font Families:

• Inter (used 17x)

Font Sizes: 8px, 11px, 12px, 14px, 15px, 16px, 18px, 19px, 20px, 75px

Spacing

• MUST use 4px grid for spacing

• SHOULD use spacing from scale: 2px, 3px, 4px, 5px, 18px

• SHOULD use 5px 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: 8px, 21px, 22px, 28px

• SHOULD use 21px+ radius for pill-shaped elements

• MUST use 1px border width consistently

• SHOULD use 21px 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: 8px, 21px, 22px, 28px

Layout

• MUST design for 1920px base viewport width

• SHOULD use consistent element widths: 72px, 61px, 27px, 78px

• SHOULD maintain text-heavy layout with clear hierarchy

• 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

• Main Content: width: 1920px, height: 850px

• Header: height: 49px

Components

Buttons

Variant Background Text Border Height Radius

Ghost transparent #4A4A4A 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 #0F0F0F background

• List items: use #0F0F0F 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