Arc UI Skills

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

When to Apply

Reference these guidelines when:

Building light-mode interfaces
Creating Arc-inspired design systems
Implementing UIs with Inter font and 4px grid

Colors

SHOULD use light backgrounds for primary surfaces
MUST use
```
#E4E4E4
```
as page background (
```
surface-base
```
)
MUST use
```
#6FADE2
```
for primary actions and focus states (
```
accent
```
)
SHOULD reduce color palette (currently 26 colors detected)
MUST maintain text contrast ratio of at least 4.5:1 for accessibility

Semantic Tokens

Token	HEX	RGB	Usage
`surface-base`	#E4E4E4	rgb(228,228,228)	Page background
`surface-raised`	#1B00B5	rgb(27,0,181)	Cards, modals, raised surfaces
`surface-overlay`	#FEFEFD	rgb(254,254,253)	Overlays, tooltips, dropdowns
`text-primary`	#BFAFEA	rgb(191,175,234)	Headings, body text
`text-secondary`	#513EA3	rgb(81,62,163)	Secondary, muted text
`text-tertiary`	#E0DCEA	rgb(224,220,234)	Additional text
`border-default`	#1902BE	rgb(25,2,190)	Subtle borders, dividers
`accent`	#6FADE2	rgb(111,173,226)	Primary actions, links, focus
`warning`	#FEFEFD	rgb(254,254,253)	Warning states, cautions

Typography

MUST use
```
Inter
```
as primary font family
SHOULD use single font family for consistency
MUST use
```
53px
```
/
```
700
```
for primary headings
MUST use
```
22px
```
/
```
500
```
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	53px	700	#E4E3EF	1
`text-36px`	Inter	36px	700	#2D2C2B	1
`body`	Inter	22px	500	#C7C7C7	1
`text-19px`	Inter	19px	400	#666664	1
`text-14px`	Inter	14px	semi_bold	#E0DCEA	1
`text-13px`	Inter	13px	400	#37556A	1
`text-13px`	Inter	13px	300	#C0C2C2	1
`text-13px`	Inter	13px	400	#AEACF0	1
`text-12px`	Inter	12px	400	#BFAFEA	1
`text-12px`	Inter	12px	400	#513EA3	1

Typography Reference

Font Families:

```
Inter
```
(used 28x)

Font Sizes: 5px, 6px, 8px, 9px, 10px, 11px, 12px, 13px, 14px, 19px, 22px, 36px, 53px

Spacing

MUST use 4px grid for spacing
SHOULD use spacing from scale: 1px, 2px, 3px, 4px, 5px, 6px, 7px, 10px
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: 2px, 3px, 4px, 5px, 6px, 7px, 8px, 9px, 21px, 22px
SHOULD use 21px+ radius for pill-shaped elements
SHOULD limit border widths to: 1px, 2px
SHOULD use 7px 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: 2px, 3px, 4px, 5px, 6px, 7px, 8px, 9px, 21px, 22px

Layout

MUST design for 1920px base viewport width
SHOULD use consistent element widths: 69px, 11px, 10px, 70px, 15px
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: 602px
Main Content: width: 1920px, height: 613px
Header: height: 99px

Components

Buttons

Variant	Background	Text	Border	Height	Radius
Ghost	transparent	#BFAFEA	none	-	-

Interactive States

Focus

MUST use
```
2px
```
outline with accent color (
```
#6FADE2
```
)
MUST use
```
2px
```
outline-offset
NEVER remove focus indicators

Hover

Buttons (primary): lighten background by 10%
Buttons (secondary): use
```
#1B00B5
```
background
List items: use
```
#1B00B5
```
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

arc-ui-skills

NPX Install

Tags

SKILL.md Content