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