Matter UI Skills

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

When to Apply

Reference these guidelines when:

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

Colors

MUST use dark backgrounds (lightness < 20) for primary surfaces - detected lightness: 0
MUST use
```
#000000
```
as page background (
```
surface-base
```
)
MUST use
```
#5560EC
```
for primary actions and focus states (
```
accent
```
)
SHOULD reduce color palette (currently 19 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`	#CFE3F9	rgb(207,227,249)	Cards, modals, raised surfaces
`surface-overlay`	#8DBDF7	rgb(141,189,247)	Overlays, tooltips, dropdowns
`text-primary`	#627EA1	rgb(98,126,161)	Headings, body text
`text-2`	#8C9BAB	rgb(140,155,171)	Additional text
`text-secondary`	#888888	rgb(136,136,136)	Secondary, muted text
`border-default`	#D4E5F8	rgb(212,229,248)	Subtle borders, dividers
`accent`	#5560EC	rgb(85,96,236)	Primary actions, links, focus
`destructive`	#200D11	rgb(32,13,17)	Error states, delete actions

Typography

MUST use
```
Inter
```
as primary font family
SHOULD use single font family for consistency
MUST use
```
81px
```
/
```
700
```
for primary headings
MUST use
```
35px
```
/
```
700
```
for body text
SHOULD reduce font weights (currently 6 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	81px	700	#F0F0F0	1
`body`	Inter	35px	700	#818181	1
`text-32px`	Inter	32px	semi_bold	#747474	1
`text-26px`	Inter	26px	extra_bold	#8C8C8C	1
`text-24px`	Inter	24px	700	#848484	1
`text-21px`	Inter	21px	semi_bold	#494949	1
`text-20px`	Inter	20px	500	#515151	1
`text-19px`	Inter	19px	400	#666666	1
`text-16px`	Inter	16px	400	#3C3C3C	1
`text-15px`	Inter	15px	400	#525252	1

Typography Reference

Font Families:

```
Inter
```
(used 32x)

Font Sizes: 8px, 9px, 10px, 11px, 12px, 13px, 14px, 15px, 16px, 19px, 20px, 21px, 24px, 26px, 32px, 35px, 81px

Spacing

MUST use 4px grid for spacing
SHOULD use spacing from scale: 1px, 2px, 4px, 5px, 6px, 7px, 9px, 10px
SHOULD use 2px 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: 0px, 1px, 10px, 15px
SHOULD limit border widths to: 1px, 2px
SHOULD use 1px 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: 0px, 1px, 10px, 15px

Layout

MUST design for 1920px base viewport width
SHOULD use consistent element widths: 13px, 102px, 38px, 37px, 14px
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

Header: height: 58px
Main Content: width: 1920px, height: 1025px
Main Content: width: 1920px, height: 1023px
Header: height: 59px

Components

Buttons

Variant	Background	Text	Border	Height	Radius
Ghost	transparent	#8C9BAB	none	-	-

Interactive States

Focus

MUST use
```
2px
```
outline with accent color (
```
#5560EC
```
)
MUST use
```
2px
```
outline-offset
NEVER remove focus indicators

Hover

Buttons (primary): lighten background by 10%
Buttons (secondary): use
```
#CFE3F9
```
background
List items: use
```
#CFE3F9
```
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

matter-ui-skills

NPX Install

Tags

SKILL.md Content