fast-next-template/frontend/docs/design-system/99-reference.md

Quick Reference

Bookmark this page for instant lookups of colors, spacing, typography, components, and common patterns. Your go-to cheat sheet for the FastNext design system.

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Table of Contents

1. Color Tokens
2. Typography Scale
3. Spacing Scale
4. Component Variants
5. Layout Patterns
6. Common Class Combinations
7. Decision Trees

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Color Tokens

Semantic Colors

Token	Usage	Example
bg-primary text-primary-foreground	CTAs, primary actions	Primary button
bg-secondary text-secondary-foreground	Secondary actions	Secondary button
bg-destructive text-destructive-foreground	Delete, errors	Delete button, error alert
bg-muted text-muted-foreground	Disabled, subtle	Disabled button, TabsList
bg-accent text-accent-foreground	Hover states	Dropdown hover
bg-card text-card-foreground	Cards, elevated surfaces	Card component
bg-popover text-popover-foreground	Popovers, dropdowns	Dropdown content
bg-background text-foreground	Page background	Body
text-foreground	Body text	Paragraphs
text-muted-foreground	Secondary text	Captions, helper text
border-border	Borders, dividers	Card borders, separators
border-input	Input borders	Text input border
ring-ring	Focus indicators	Focus ring

Usage Examples

// Primary button
<Button className="bg-primary text-primary-foreground">Save</Button>

// Destructive button
<Button className="bg-destructive text-destructive-foreground">Delete</Button>

// Secondary text
<p className="text-muted-foreground text-sm">Helper text</p>

// Card
<Card className="bg-card text-card-foreground border-border">...</Card>

// Focus ring
<div className="focus-visible:ring-2 focus-visible:ring-ring">...</div>

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Typography Scale

Font Sizes

Class	rem	px	Use Case	Common
text-xs	0.75rem	12px	Labels, fine print
text-sm	0.875rem	14px	Secondary text, captions	⭐
text-base	1rem	16px	Body text (default)	⭐
text-lg	1.125rem	18px	Subheadings
text-xl	1.25rem	20px	Card titles	⭐
text-2xl	1.5rem	24px	Section headings	⭐
text-3xl	1.875rem	30px	Page titles	⭐
text-4xl	2.25rem	36px	Large headings
text-5xl	3rem	48px	Hero text

⭐ = Most commonly used

Font Weights

Class	Value	Use Case	Common
font-light	300	De-emphasized text
font-normal	400	Body text (default)	⭐
font-medium	500	Labels, menu items	⭐
font-semibold	600	Subheadings, buttons	⭐
font-bold	700	Headings, emphasis	⭐

⭐ = Most commonly used

Common Typography Combinations

// Page title
<h1 className="text-3xl font-bold">Page Title</h1>

// Section heading
<h2 className="text-2xl font-semibold mb-4">Section Heading</h2>

// Card title
<h3 className="text-xl font-semibold">Card Title</h3>

// Body text (default)
<p className="text-base text-foreground">Regular paragraph</p>

// Secondary text
<p className="text-sm text-muted-foreground">Helper text</p>

// Label
<Label className="text-sm font-medium">Field Label</Label>

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Spacing Scale

Spacing Values

Token	rem	px	Use Case	Common
0	0	0px	No spacing
px	-	1px	Borders
0.5	0.125rem	2px	Very tight
1	0.25rem	4px	Icon gaps
2	0.5rem	8px	Tight spacing (label → input)	⭐
3	0.75rem	12px	Component padding
4	1rem	16px	Standard spacing (form fields)	⭐
5	1.25rem	20px	Medium spacing
6	1.5rem	24px	Section spacing (cards)	⭐
8	2rem	32px	Large gaps	⭐
10	2.5rem	40px	Very large gaps
12	3rem	48px	Section dividers	⭐
16	4rem	64px	Page sections

⭐ = Most commonly used

Spacing Methods

Method	Use Case	Example
gap-4	Flex/grid spacing	flex gap-4
space-y-4	Vertical stack spacing	space-y-4
space-x-4	Horizontal stack spacing	space-x-4
p-4	Padding (all sides)	p-4
px-4	Horizontal padding	px-4
py-4	Vertical padding	py-4
m-4	Margin (exceptions only!)	mt-8

Common Spacing Patterns

// Form vertical spacing
<form className="space-y-4">...</form>

// Field group spacing (label → input)
<div className="space-y-2">
  <Label>...</Label>
  <Input />
</div>

// Button group horizontal spacing
<div className="flex gap-4">
  <Button>Cancel</Button>
  <Button>Save</Button>
</div>

// Card grid spacing
<div className="grid grid-cols-3 gap-6">...</div>

// Page padding
<div className="container mx-auto px-4 py-8">...</div>

// Card padding
<Card className="p-6">...</Card>

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Component Variants

Button Variants

<Button variant="default">Primary</Button>
<Button variant="secondary">Secondary</Button>
<Button variant="outline">Outline</Button>
<Button variant="ghost">Ghost</Button>
<Button variant="link">Link</Button>
<Button variant="destructive">Delete</Button>

<Button size="sm">Small</Button>
<Button size="default">Default</Button>
<Button size="lg">Large</Button>
<Button size="icon"><Icon /></Button>

Badge Variants

<Badge variant="default">New</Badge>
<Badge variant="secondary">Draft</Badge>
<Badge variant="outline">Pending</Badge>
<Badge variant="destructive">Critical</Badge>

Alert Variants

<Alert variant="default">Info alert</Alert>
<Alert variant="destructive">Error alert</Alert>

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Layout Patterns

Grid Columns

// 1 → 2 → 3 progression (most common)
className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6"

// 1 → 2 → 4 progression
className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-6"

// 1 → 2 progression (simple)
className="grid grid-cols-1 md:grid-cols-2 gap-6"

// 1 → 3 progression (skip 2)
className="grid grid-cols-1 lg:grid-cols-3 gap-6"

Container Widths

// Standard container
className="container mx-auto px-4"

// Constrained widths
className="max-w-md mx-auto"   // 448px - Forms
className="max-w-lg mx-auto"   // 512px - Modals
className="max-w-2xl mx-auto"  // 672px - Articles
className="max-w-4xl mx-auto"  // 896px - Wide layouts
className="max-w-7xl mx-auto"  // 1280px - Full page

Flex Patterns

// Horizontal flex
className="flex gap-4"

// Vertical flex
className="flex flex-col gap-4"

// Center items
className="flex items-center justify-center"

// Space between
className="flex items-center justify-between"

// Wrap items
className="flex flex-wrap gap-4"

// Responsive: stack on mobile, row on desktop
className="flex flex-col sm:flex-row gap-4"

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Common Class Combinations

Page Container

<div className="container mx-auto px-4 py-8">
  <div className="max-w-4xl mx-auto space-y-6">
    {/* Content */}
  </div>
</div>

Card Header with Action

<CardHeader className="flex flex-row items-center justify-between space-y-0">
  <div>
    <CardTitle>Title</CardTitle>
    <CardDescription>Description</CardDescription>
  </div>
  <Button variant="outline" size="sm">Action</Button>
</CardHeader>

Dashboard Metric Card Header

<CardHeader className="flex flex-row items-center justify-between space-y-0 pb-2">
  <CardTitle className="text-sm font-medium">Metric Title</CardTitle>
  <Icon className="h-4 w-4 text-muted-foreground" />
</CardHeader>

Form Field

<div className="space-y-2">
  <Label htmlFor="field">Label</Label>
  <Input id="field" />
  {error && <p className="text-sm text-destructive">{error.message}</p>}
</div>

Centered Form Card

<div className="container mx-auto px-4 py-8">
  <Card className="max-w-md mx-auto">
    <CardHeader>
      <CardTitle>Form Title</CardTitle>
    </CardHeader>
    <CardContent>
      <form className="space-y-4">
        {/* Fields */}
      </form>
    </CardContent>
  </Card>
</div>

Button Group

<div className="flex gap-4">
  <Button variant="outline">Cancel</Button>
  <Button>Save</Button>
</div>

// Or right-aligned
<div className="flex justify-end gap-4">
  <Button variant="outline">Cancel</Button>
  <Button>Save</Button>
</div>

Icon with Text

<div className="flex items-center gap-2">
  <Icon className="h-4 w-4" />
  <span>Text</span>
</div>

Responsive Text

<h1 className="text-2xl sm:text-3xl lg:text-4xl font-bold">
  Responsive Title
</h1>

Responsive Padding

<div className="p-4 sm:p-6 lg:p-8">
  Responsive padding
</div>

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Decision Trees

Grid vs Flex

Need equal-width columns? → Grid
  Example: grid grid-cols-3 gap-6

Need flexible item sizes? → Flex
  Example: flex gap-4

Need 2D layout (rows + columns)? → Grid
  Example: grid grid-cols-2 grid-rows-3 gap-4

Need 1D layout (row OR column)? → Flex
  Example: flex flex-col gap-4

Margin vs Padding vs Gap

Spacing between siblings?
  ├─ Flex/Grid parent? → gap
  └─ Regular parent? → space-y or space-x

Inside component? → padding

Exception case (one child different)? → margin

Button Variant

What's the action?
├─ Primary action (save, submit) → variant="default"
├─ Secondary action (cancel, back) → variant="secondary"
├─ Alternative action (view, edit) → variant="outline"
├─ Subtle action (icon in list) → variant="ghost"
├─ In-text action (learn more) → variant="link"
└─ Delete/remove action → variant="destructive"

Form Field Error Display

Has error?
  ├─YES─> Add aria-invalid={true}
  │       Add aria-describedby="field-error"
  │       Add border-destructive class
  │       Show <p id="field-error" className="text-sm text-destructive">
  │
  └─NO──> Normal state

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Keyboard Shortcuts

Key	Action	Context
Tab	Move focus forward	All
Shift + Tab	Move focus backward	All
Enter	Activate button/link	Buttons, links
Space	Activate button/checkbox	Buttons, checkboxes
Escape	Close overlay	Dialogs, dropdowns
Arrow keys	Navigate items	Dropdowns, lists
Home	Jump to start	Lists
End	Jump to end	Lists

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Accessibility Quick Checks

Contrast Ratios

• Normal text (< 18px): 4.5:1 minimum
• Large text (≥ 18px or ≥ 14px bold): 3:1 minimum
• UI components: 3:1 minimum

ARIA Attributes

// Icon-only button
<Button size="icon" aria-label="Close">
  <X className="h-4 w-4" />
</Button>

// Form field error
<Input
  aria-invalid={!!error}
  aria-describedby={error ? 'field-error' : undefined}
/>
{error && <p id="field-error">{error.message}</p>}

// Required field
<Input aria-required="true" required />

// Live region
<div aria-live="polite">{statusMessage}</div>

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Import Cheat Sheet

// Components
import { Button } from '@/components/ui/button';
import { Card, CardHeader, CardTitle, CardContent } from '@/components/ui/card';
import { Input } from '@/components/ui/input';
import { Label } from '@/components/ui/label';
import { Alert, AlertDescription, AlertTitle } from '@/components/ui/alert';
import { Dialog, DialogContent, DialogHeader, DialogTitle } from '@/components/ui/dialog';
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';
import { Tabs, TabsList, TabsTrigger, TabsContent } from '@/components/ui/tabs';

// Utilities
import { cn } from '@/lib/utils';

// Form
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';

// Toast
import { toast } from 'sonner';

// Icons
import { Check, X, AlertCircle, Loader2 } from 'lucide-react';

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Zod Validation Patterns

// Required string
z.string().min(1, 'Required')

// Email
z.string().email('Invalid email')

// Min/max length
z.string().min(8, 'Min 8 chars').max(100, 'Max 100 chars')

// Optional
z.string().optional()

// Number
z.coerce.number().min(0).max(100)

// Enum
z.enum(['admin', 'user', 'guest'])

// Boolean
z.boolean().refine(val => val === true, { message: 'Must accept' })

// Password confirmation
z.object({
  password: z.string().min(8),
  confirmPassword: z.string()
}).refine(data => data.password === data.confirmPassword, {
  message: "Passwords don't match",
  path: ["confirmPassword"],
})

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Responsive Breakpoints

Breakpoint	Min Width	Typical Device
sm:	640px	Large phones, small tablets
md:	768px	Tablets
lg:	1024px	Laptops, desktops
xl:	1280px	Large desktops
2xl:	1536px	Extra large screens

// Mobile-first (default → sm → md → lg)
className="text-sm sm:text-base md:text-lg lg:text-xl"
className="p-4 sm:p-6 lg:p-8"
className="grid-cols-1 md:grid-cols-2 lg:grid-cols-3"

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Shadows & Radius

Shadows

shadow-sm   // Cards, panels
shadow-md   // Dropdowns, tooltips
shadow-lg   // Modals, popovers
shadow-xl   // Floating notifications

Border Radius

rounded-sm   // 2px - Tags, small badges
rounded-md   // 4px - Inputs, small buttons
rounded-lg   // 6px - Cards, buttons (default)
rounded-xl   // 10px - Large cards, modals
rounded-full // Pills, avatars, icon buttons

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Next Steps

• For detailed info: Navigate to specific guides from README
• For examples: Visit /dev/components
• For AI: See AI Guidelines

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Related Documentation:

• Quick Start - 5-minute crash course
• Foundations - Detailed color, typography, spacing
• Components - All component variants
• Layouts - Layout patterns
• Forms - Form patterns
• Accessibility - WCAG compliance

Last Updated: November 2, 2025