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

mercury-ui-skills

NPX Install

Tags

SKILL.md Content