Mercury UI Skills

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

When to Apply

Reference these guidelines when:

• Building light-mode interfaces

• Creating Mercury-inspired design systems

• Implementing UIs with Inter font and 4px grid

Colors

• SHOULD use light backgrounds for primary surfaces

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

• MUST use #8B9CEC for primary actions and focus states (accent )

• SHOULD reduce color palette (currently 23 colors detected)

• 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

#FFFFFF rgb(255,255,255) Cards, modals, raised surfaces

surface-overlay

#ECEDEE rgb(236,237,238) Overlays, tooltips, dropdowns

text-primary

#C2C2C2 rgb(194,194,194) Headings, body text

text-secondary

#B0B0B0 rgb(176,176,176) Secondary, muted text

text-tertiary

#D0D0D7 rgb(208,208,215) Additional text

border-default

#FDFEFE rgb(253,254,254) Subtle borders, dividers

accent

#8B9CEC rgb(139,156,236) Primary actions, links, focus

Typography

• MUST use Inter as primary font family

• SHOULD use single font family for consistency

• MUST use 69px / 700 for primary headings

• MUST use 16px / 700 for body text

• SHOULD reduce font weights (currently 5 detected)

• 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 69px 700 #32312D 1

text-26px

Inter 26px 500 #4C4E4D 1

text-25px

Inter 25px 400 #5C5B5E 1

text-21px

Inter 21px 400 #726F69 1

body

Inter 16px 700 #BBBCBF 1

body-secondary

Inter 15px 400 #A9A9A9 1

body-secondary

Inter 15px 400 #A8A8A8 1

body-secondary

Inter 15px 400 #AAAAAA 1

body-secondary

Inter 15px 400 #C4C6C5 1

body-secondary

Inter 15px 400 #B1BBF3 1

Typography Reference

Font Families:

• Inter (used 56x)

Font Sizes: 9px, 11px, 12px, 13px, 14px, 15px, 16px, 21px, 25px, 26px, 69px

Spacing

• MUST use 4px grid for spacing

• SHOULD use spacing from scale: 2px, 4px, 5px, 6px, 7px, 10px, 11px, 12px

• 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: 3px, 4px, 10px, 13px, 16px, 18px, 21px

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

• SHOULD limit border widths to: 1px, 2px, 5px, 7px

• SHOULD use 13px 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, 4px, 10px, 13px, 16px, 18px, 21px

Layout

• MUST design for 1920px base viewport width

• SHOULD use consistent element widths: 11px, 8px, 12px, 9px, 13px

• 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: 563px

• Main Content: width: 1920px, height: 625px

• Main Content: width: 1352px, height: 605px

• Main Content: width: 1139px, height: 595px

• Header: height: 67px

Components

• MUST use 0px height for input fields

Buttons

Variant Background Text Border Height Radius

Ghost transparent #8E9090 none

Inputs

• Height: 0px

Interactive States

Focus

• MUST use 2px outline with accent color (#8B9CEC )

• MUST use 2px outline-offset

• NEVER remove focus indicators

Hover

• Buttons (primary): lighten background by 10%

• Buttons (secondary): use #FFFFFF background

• List items: use #FFFFFF 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