Cal UI Skills

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

When to Apply

Reference these guidelines when:

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

Colors

SHOULD use light backgrounds for primary surfaces
MUST use
```
#FDFDFD
```
as page background (
```
surface-base
```
)
SHOULD reduce color palette (currently 16 colors detected)
MUST maintain text contrast ratio of at least 4.5:1 for accessibility

Semantic Tokens

Token	HEX	RGB	Usage
`surface-base`	#FDFDFD	rgb(253,253,253)	Page background
`surface-raised`	#EDEDED	rgb(237,237,237)	Cards, modals, raised surfaces
`surface-overlay`	#1C1C1C	rgb(28,28,28)	Overlays, tooltips, dropdowns
`text-primary`	#6B6B6B	rgb(107,107,107)	Headings, body text
`text-secondary`	#A1A1A1	rgb(161,161,161)	Secondary, muted text
`text-tertiary`	#404040	rgb(64,64,64)	Additional text
`border-default`	#E5E5E5	rgb(229,229,229)	Subtle borders, dividers
`destructive`	#FCC9C1	rgb(252,201,193)	Error states, delete actions

Typography

MUST use
```
Inter
```
as primary font family
SHOULD use single font family for consistency
MUST use
```
70px
```
/
```
700
```
for primary headings
MUST use
```
16px
```
/
```
400
```
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	70px	700	#2A2A2A	1
`text-23px`	Inter	23px	semi_bold	#C1C1C1	1
`text-22px`	Inter	22px	semi_bold	#494949	1
`text-21px`	Inter	21px	500	#676767	1
`text-21px`	Inter	21px	semi_bold	#383838	1
`text-19px`	Inter	19px	500	#2C2C2C	1
`text-19px`	Inter	19px	500	#3C3C3C	1
`text-19px`	Inter	19px	500	#D4D4D4	1
`text-18px`	Inter	18px	500	#404040	1
`body`	Inter	16px	400	#A4A4A4	1

Typography Reference

Font Families:

```
Inter
```
(used 65x)

Font Sizes: 8px, 9px, 10px, 11px, 12px, 13px, 14px, 15px, 16px, 18px, 19px, 21px, 22px, 23px, 70px

Spacing

MUST use 4px grid for spacing
SHOULD use spacing from scale: 1px, 2px, 3px, 4px, 5px, 6px, 7px, 9px
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: 1px, 2px, 3px, 4px, 6px, 7px, 8px, 9px, 10px, 11px
SHOULD limit border widths to: 1px, 3px
SHOULD use 3px 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: 1px, 2px, 3px, 4px, 6px, 7px, 8px, 9px, 10px, 11px

Layout

MUST design for 1920px base viewport width
SHOULD use consistent element widths: 16px, 8px, 11px, 10px, 52px
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: 1565px, height: 814px
Main Content: width: 1920px, height: 1080px
Main Content: width: 1180px, height: 717px
Main Content: width: 1178px, height: 701px

Components

Buttons

Variant	Background	Text	Border	Height	Radius
Ghost	transparent	#6B6B6B	none	-	-

Interactive States

Focus

MUST use
```
2px
```
outline with accent color (
```
#5E6AD2
```
)
MUST use
```
2px
```
outline-offset
NEVER remove focus indicators

Hover

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

cal-ui-skills

NPX Install

Tags

SKILL.md Content