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:
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
1---2name: cal-ui-skills3description: Cal's UI design system. Use when building interfaces inspired by Cal's aesthetic - light mode, Inter font, 4px grid.4license: MIT5---6
7# Cal UI Skills
8
9Opinionated constraints for building Cal-style interfaces with AI agents.
10
11## When to Apply
12
13Reference these guidelines when:
14- Building light-mode interfaces
15- Creating Cal-inspired design systems
16- Implementing UIs with Inter font and 4px grid
17
18## Colors
19
20- SHOULD use light backgrounds for primary surfaces
21- MUST use `#FDFDFD` as page background (`surface-base`)
22- SHOULD reduce color palette (currently 16 colors detected)
23- MUST maintain text contrast ratio of at least 4.5:1 for accessibility
24
25### Semantic Tokens
26
27| Token | HEX | RGB | Usage |
28|-------|-----|-----|-------|
29| `surface-base` | #FDFDFD | rgb(253,253,253) | Page background |
30| `surface-raised` | #EDEDED | rgb(237,237,237) | Cards, modals, raised surfaces |
31| `surface-overlay` | #1C1C1C | rgb(28,28,28) | Overlays, tooltips, dropdowns |
32| `text-primary` | #6B6B6B | rgb(107,107,107) | Headings, body text |
33| `text-secondary` | #A1A1A1 | rgb(161,161,161) | Secondary, muted text |
34| `text-tertiary` | #404040 | rgb(64,64,64) | Additional text |
35| `border-default` | #E5E5E5 | rgb(229,229,229) | Subtle borders, dividers |
36| `destructive` | #FCC9C1 | rgb(252,201,193) | Error states, delete actions |
37
38## Typography
39
40- MUST use `Inter` as primary font family
41- SHOULD use single font family for consistency
42- MUST use `70px` / `700` for primary headings
43- MUST use `16px` / `400` for body text
44- SHOULD reduce font weights (currently 5 detected)
45- MUST use `text-balance` for headings and `text-pretty` for body text
46- SHOULD use `tabular-nums` for numeric data
47- NEVER modify letter-spacing unless explicitly requested
48
49### Text Styles
50
51| Style | Font | Size | Weight | Color | Count |
52|-------|------|------|--------|-------|-------|
53| `heading-1` | Inter | 70px | 700 | #2A2A2A | 1 |
54| `text-23px` | Inter | 23px | semi_bold | #C1C1C1 | 1 |
55| `text-22px` | Inter | 22px | semi_bold | #494949 | 1 |
56| `text-21px` | Inter | 21px | 500 | #676767 | 1 |
57| `text-21px` | Inter | 21px | semi_bold | #383838 | 1 |
58| `text-19px` | Inter | 19px | 500 | #2C2C2C | 1 |
59| `text-19px` | Inter | 19px | 500 | #3C3C3C | 1 |
60| `text-19px` | Inter | 19px | 500 | #D4D4D4 | 1 |
61| `text-18px` | Inter | 18px | 500 | #404040 | 1 |
62| `body` | Inter | 16px | 400 | #A4A4A4 | 1 |
63
64### Typography Reference
65
66**Font Families:**
67- `Inter` (used 65x)
68
69**Font Sizes:** 8px, 9px, 10px, 11px, 12px, 13px, 14px, 15px, 16px, 18px, 19px, 21px, 22px, 23px, 70px
70
71## Spacing
72
73- MUST use 4px grid for spacing
74- SHOULD use spacing from scale: 1px, 2px, 3px, 4px, 5px, 6px, 7px, 9px
75- SHOULD use 5px as default gap between elements
76- NEVER use arbitrary spacing values (use design scale)
77- SHOULD maintain consistent padding within containers
78
79## Borders
80
81- MUST use border-radius from scale: 1px, 2px, 3px, 4px, 6px, 7px, 8px, 9px, 10px, 11px
82- SHOULD limit border widths to: 1px, 3px
83- SHOULD use 3px as default border-radius
84- NEVER use arbitrary border-radius values (use design scale)
85- SHOULD use subtle borders (1px) for element separation
86
87### Border Radius Reference
88
89**Scale:** 1px, 2px, 3px, 4px, 6px, 7px, 8px, 9px, 10px, 11px
90
91## Layout
92
93- MUST design for 1920px base viewport width
94- SHOULD use consistent element widths: 16px, 8px, 11px, 10px, 52px
95- SHOULD maintain text-heavy layout with clear hierarchy
96- NEVER use `h-screen`, use `h-dvh` for full viewport height
97- MUST respect `safe-area-inset` for fixed elements
98- SHOULD use `size-*` for square elements instead of `w-*` + `h-*`
99
100### Detected Layout Patterns
101
102- **Main Content**: width: 1565px, height: 814px
103- **Main Content**: width: 1920px, height: 1080px
104- **Main Content**: width: 1180px, height: 717px
105- **Main Content**: width: 1178px, height: 701px
106
107## Components
108
109### Buttons
110
111| Variant | Background | Text | Border | Height | Radius |
112|---------|------------|------|--------|--------|--------|
113| Ghost | transparent | #6B6B6B | none | - | - |
114
115## Interactive States
116
117### Focus
118
119- MUST use `2px` outline with accent color (`#5E6AD2`)
120- MUST use `2px` outline-offset
121- NEVER remove focus indicators
122
123### Hover
124
125- Buttons (primary): lighten background by 10%
126- Buttons (secondary): use `#EDEDED` background
127- List items: use `#EDEDED` background
128
129### Disabled
130
131- MUST use `opacity: 0.5`
132- MUST use `cursor: not-allowed`
133
134## Interaction
135
136- MUST use an `AlertDialog` for destructive or irreversible actions
137- SHOULD use structural skeletons for loading states
138- MUST show errors next to where the action happens
139- NEVER block paste in `input` or `textarea` elements
140- MUST add an `aria-label` to icon-only buttons
141
142## Animation
143
144- NEVER add animation unless it is explicitly requested
145- MUST animate only compositor props (`transform`, `opacity`)
146- NEVER animate layout properties (`width`, `height`, `top`, `left`, `margin`, `padding`)
147- SHOULD use `ease-out` on entrance animations
148- NEVER exceed `200ms` for interaction feedback
149- SHOULD respect `prefers-reduced-motion`
150
151## Performance
152
153- NEVER animate large `blur()` or `backdrop-filter` surfaces
154- NEVER apply `will-change` outside an active animation
155- NEVER use `useEffect` for anything that can be expressed as render logic
ihlamury