Casper Design System

Casper Studios Design System

A clean, elevated SaaS design system built on shadcn/ui, Tailwind CSS v4, and React (Vite). Every interface generated for Casper Studios — whether a client demo, internal tool, or quick prototype — must follow these rules to maintain a consistent, professional visual identity across the team.

Before generating any UI code, read this file completely and the reference files listed below. You MUST read the reference files — they contain rules and code examples that are required for correct output. Skipping them will produce incorrect, off-brand UI.

Required for EVERY project:

• references/components.md — ALWAYS read. Reusable pieces: stat cards, list items, filter bars, kanban boards, profile cards, product cards, activity feeds, toast notifications, form validation states. Required whenever building UI elements inside a layout.
• references/theme.css — ALWAYS read. Tailwind CSS v4 theme tokens. Copy this file into your project as-is.
• assets/ — Contains Casper Studios logo SVGs in 4 variants (default, variant, mono-black, mono-white). Use the correct variant based on background color — see the Logo section below.

Required based on platform:

• references/web-layouts.md — MUST read when the project is a web application. Web-specific responsive rules + code examples: app shell, sidebar nav, dashboard grid, data table page, page header.
• references/mobile.md — MUST read when the project is a mobile application. Mobile-specific rules + code examples: device frame, top bar, bottom tab navigation, form patterns, pinned-button layout, list views, card stacks, full screen compositions, contextual actions (menus + bottom sheets).

Non-negotiable: Do not generate UI without reading the platform reference file first. If you are unsure whether the project is web or mobile, ask the user before proceeding.

Before You Generate: Required Context

Before producing any UI code, confirm the following with the user. If their prompt already answers these clearly, proceed without asking. If not, ask before generating anything.

1. Platform — Is this a web application or a mobile application? (Determines which reference file to follow.)
2. Dark mode — Should the interface support dark mode, or is it light mode only? (Determines whether to implement .dark class overrides, use bg-neutral-0 for surfaces, and include the mono-white logo variant.)

Do NOT assume defaults for these. If the user says "build me a dashboard," you don't know if it's web or mobile, or if it needs dark mode. Ask.

Summary

The Casper aesthetic is clean authority — a professional SaaS style that feels premium without trying too hard. It uses generous whitespace, a restrained purple accent, and soft rounded surfaces to create interfaces that feel trustworthy and modern. Think Linear meets Notion: structured, breathable, quietly confident.

Core Principles

1. Whitespace is a feature. Generous padding, breathing room between sections. Never cram.
2. One accent, used sparingly. Brand purple (#5900FF) appears on active states, primary buttons, and key CTAs — nowhere else. If everything is purple, nothing is.
3. Rounded but not bubbly. 10px default radius for cards (shadcn default). Buttons and inputs use 8px. Feels modern without feeling like a toy.
4. Flat with depth hints. No heavy shadows. Use shadow-sm for cards, shadow-md for popovers. Never use shadow-lg on in-page elements.
5. Content over chrome. The UI should disappear. Users notice the data, not the design.

Tech Stack

• React (Vite) with TypeScript
• Tailwind CSS v4 — Use the theme file at references/theme.css as Casper brand overrides
• shadcn/ui — Initialize a standard shadcn/ui project first (shadcn init), then layer Casper brand tokens from references/theme.css on top. The shadcn semantic layer (bg-background, text-foreground, bg-primary, border-border, etc.) is the base — Casper's theme.css adds brand colors, typography, shadows, and spacing on top of it, not as a replacement. Use shadcn components directly. Do NOT create custom base components that duplicate shadcn functionality
• Lucide React — Icon library. Always use Lucide, never Heroicons or FontAwesome
• Fonts — DM Sans with sans-serif as fallback for all UI text. Load via Google Fonts or bundle

Color System

The palette is intentionally restrained. Most of the UI is neutral gray + white, with purple as a sharp accent.

Usage Rules

Semantic Colors

Use these ONLY for status indicators, badges, and contextual feedback — never as decorative accents.

• Success — success-500 (#22C55E) for badges/icons, success-50 for pill backgrounds
• Error — error-500 (#EF4444) for badges/icons, error-50 for pill backgrounds
• Warning — warning-500 (#F59E0B) for badges/icons, warning-50 for pill backgrounds

What NOT to do

• Do NOT use brand purple for backgrounds on large surfaces
• Do NOT use semantic colors decoratively
• Do NOT introduce new colors. If you need a new shade, use the neutral scale
• Do NOT use opacity-based colors when a token exists (e.g., don't do text-black/50, use neutral-500)

Typography

All text is set in DM Sans with sans-serif as fallback (font-family: 'DM Sans', sans-serif). Monospace (font-mono) is acceptable for code blocks, data labels, and IDs only.

Scale

Rules

• Headings are always medium weight (500), never bold (700)
• NEVER use all-caps except for tiny metadata labels (e.g., "STATUS", "OWNER" in table column headers) set at caption size
• Links use brand-500 color with no underline by default, underline on hover
• Do NOT vary font size beyond this scale. If something feels wrong, adjust spacing not font size

Spacing & Layout

Spacing Scale

Use Tailwind's default spacing scale. Key values:

• 4px (p-1) — icon padding, tight gaps
• 8px (p-2) — badge padding, small gaps
• 12px (p-3) — input padding, card internal gaps
• 16px (p-4) — card padding, section gaps
• 24px (p-6) — between cards, content sections
• 32px (p-8) — major section separation
• 48px (p-12) — page-level padding on large screens

Layout Rules

• Page background: neutral-50 (#FAFAFA)
• Content is always organized inside Cards (white background, border, rounded)
• Maximum content width: 1280px centered
• On pages with a sidebar, sidebar is 240px fixed width
• Main content area uses remaining space with 24px padding

Shadows & Elevation

The design is predominantly flat. Shadows are used to indicate layers, not to add decoration.

NEVER apply shadow-lg (or its alias shadow-overlay) to cards or in-page elements. These are reserved for floating layers only.

Border Radius

The theme file (references/theme.css) uses the shadcn/ui radius system — a single --radius base variable in :root that controls the entire scale via calc(). This is mapped into Tailwind classes via @theme inline. No Tailwind v4 defaults are overridden.

The base value --radius: 0.625rem (10px) is the shadcn default. To make the entire UI sharper or rounder, change this single value — all tokens recalculate automatically.

Cards always use rounded-lg (10px). Buttons and inputs always use rounded-md (8px). Nested elements inside cards should use rounded-sm (6px) for non-interactive elements to maintain visual hierarchy — the inner radius should always be smaller than the outer.

Iconography

• Use Lucide React exclusively. Import as: import { IconName } from "lucide-react"
• Default icon size: 16px for inline, 20px for standalone
• Icon color follows its text context (e.g., neutral-500 for subtext, brand-500 for active)
• For icons inside circular backgrounds (common in lists and dashboards):
  • Circle: 40px diameter, brand-50 or brand-100 background, rounded-full
  • Icon: 20px, brand-500 color
  • For semantic contexts, swap to the matching semantic color pair (e.g., error-50 bg + error-500 icon)

Casper Studios Logo

The Casper Studios logo has four variants stored in assets/. Use the correct variant based on the background it sits on:

Rules

• Light mode (default): Use logo-on-white-default.svg or logo-on-white-variant.svg
• Dark mode or dark surfaces: Use logo-mono-white.svg — never place the default or black logo on a dark background
• The logo should appear in the sidebar header (web) or top bar (mobile) at the sizes defined in those patterns
• Do NOT resize the logo disproportionately — maintain the original aspect ratio
• Do NOT place the logo on busy backgrounds or low-contrast surfaces. If contrast is insufficient, use the mono variant that provides the best visibility
• Minimum clear space around the logo: 8px on all sides

shadcn/ui Component Theming

Use shadcn/ui components as your base layer. Theme them using the CSS variables in references/theme.css. Here is how specific components should be configured:

Button

• Primary: brand-500 bg, text-white (literal white, not a token), rounded-md. Hover: brand-600.
• Secondary: White bg, neutral-200 border, neutral-900 text, rounded-md. Hover: neutral-50 bg.
• Ghost: No bg, no border. neutral-600 text, rounded-md. Hover: neutral-100 bg.
• Destructive: error-500 bg, text-white, rounded-md.
• All buttons: rounded-md (8px), 14px font.
• Default height: 48px (h-12). Use this on standalone pages, forms, modals, and any top-level content area.
• Compact height: 36px (h-9). Use when the button lives inside a smaller container — cards, panels, table rows, sidebar nav, filter bars, inline actions. The tighter context calls for a tighter control.

Badge

• rounded-full (pill shape). Height 22px. Caption-bold text (12px, 500 weight).
• Semantic badges: Use pastel bg + darker text. E.g., success badge = success-50 bg, success-700 text.
• Neutral badge: neutral-100 bg, neutral-700 text.
• Brand badge: brand-50 bg, brand-700 text.
• Always include a small dot or icon before the label when indicating status.

Card

• White background (bg-neutral-0). 1px neutral-200 border. rounded-lg (10px). shadow-sm.
• Internal padding: 16px minimum, 24px for spacious cards.
• Card headers: Heading 3 (16px/500) with optional "View all" link aligned right.
• Separate header from content with a 1px neutral-200 divider.

Table

• Use shadcn <Table>. No outer border on the table itself — let the parent Card provide the container.
• Column headers: Caption-bold (12px/500), neutral-500 color, uppercase.
• Row height: 48-56px. Rows separated by 1px neutral-200 bottom border.
• Row hover: neutral-50 background.
• No alternating row colors.

Input / Textarea

• rounded-md (8px). 1px neutral-200 border. neutral-50 bg or white bg.
• Focus: 2px brand-500 ring (use Tailwind ring-2 ring-brand-500).
• Labels MUST be visible and external — render a <label> element above every input, never inside it. Labels use 14px/400 in neutral-900. The gap between label and input is 6px (space-y-1.5).
• Placeholder text MUST be de-emphasized — neutral-400 color, normal weight (400), short hint text (e.g., "e.g. john@email.com"). Placeholders are supplementary hints, not labels.
• Select inputs follow the same pattern: visible label above, de-emphasized placeholder inside.
• Spacing between fields: 16px (space-y-4 or gap-4).
• Default height: 48px (h-12). Use for inputs on standalone pages, forms, modals, and any top-level content area.
• Compact height: 36px (h-9). Use when the input lives inside a smaller container — cards, panels, table rows, filter bars, inline search fields. Same logic as compact buttons.

Sidebar (App Shell)

See references/web-layouts.md for the full sidebar code pattern. Key specs:

• Width: 240px. White background. Right border: 1px neutral-200.
• Nav items: 36px height (compact — inside sidebar panel), rounded-sm (6px), 12px left padding.
  • Default: neutral-600 text. Active: brand-50 bg, brand-500 text, font-weight: 500. Hover: neutral-100 bg.
• Group labels: Caption (12px/400), neutral-400, 24px top margin between groups.
• On mobile: Sidebar collapses to a Sheet (slide-in from left).

Tabs

• Use shadcn <Tabs>. Underline variant.
• Active tab: brand-500 bottom border (2px), neutral-900 text.
• Inactive tab: no border, neutral-500 text. Hover: neutral-900 text.

Dialog / Sheet

• Overlay: black/50 opacity.
• Container: white bg, rounded-xl (14px), shadow-overlay.
• Always include a close button (X icon) top-right.

Composite Patterns

For rules and code examples, read the appropriate reference file:

• references/web-layouts.md — Responsive rules, App Shell, Sidebar Navigation, Dashboard Grid, Data Table Page, Page Header
• references/components.md — Stat Card, List Item Row, Filter Bar, Kanban Board, Profile/Discovery Card, Product Card, Activity Feed Item, Toast Notifications, Form Validation States
• references/mobile.md — Mobile rules, Device Frame Shell, Mobile Top Bar, Bottom Tab Navigation, Mobile Form Layout, Pinned Bottom Button, Mobile List View, Mobile Card Stack, Full Screen Composition, Contextual Actions

Web vs Mobile Context

Every project is either a web application or a mobile application — the layout approach is fundamentally different. You MUST have already read the appropriate platform reference file (as instructed at the top of this document) before reaching this point. If you haven't, stop and read it now:

• Web application → references/web-layouts.md (responsive breakpoints, sidebar behavior, layout patterns)
• Mobile application (native app, iOS, Android, phone-based experience) → references/mobile.md (device frame, touch targets, pinned buttons, navigation, mobile-specific rules)

Do NOT treat a mobile app as a responsive web page. Mobile apps render inside a device frame and follow entirely different navigation, spacing, and interaction patterns.

Image Placeholders

When no real image is available, use soft gradient mesh backgrounds — NOT gray boxes. These should feel like abstract art, not loading states.

Gradient recipes (CSS linear-gradient or radial-gradient combos):

• Mint/Teal: linear-gradient(135deg, #a8edea 0%, #fed6e3 50%, #a8edea 100%)
• Peach/Coral: linear-gradient(135deg, #f6d5c5 0%, #e8b4b8 50%, #d4a0a0 100%)
• Purple/Pink: linear-gradient(135deg, #c3b1e1 0%, #f0c4d0 50%, #e0aed0 100%)
• Teal/Emerald: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%)

Apply rounded-lg to image containers. These are placeholders — they should look intentional and beautiful.

Transitions & Animations

Every state change should feel smooth and intentional — no hard cuts. This applies across both web and mobile:

• Interactive elements (buttons, inputs, cards): Use transition-colors or transition-all with Tailwind's default duration (~150ms). State changes like hover, focus, and active should never feel instantaneous.
• Page transitions: When navigating between views, apply a subtle slide or fade. A 150–300ms ease-out transition keeps things feeling responsive without sluggish.
• Modals, Dialogs, Sheets: Always animate in and out. Sheets slide from their edge (left, right, bottom), dialogs/modals fade + scale up slightly from ~95% to 100%. The overlay backdrop should fade in (opacity 0→50%), not appear instantly.
• Lists and content loading: When new items appear (e.g., after a fetch), a subtle fade-in or stagger is preferred over a hard pop-in.

Nothing on screen should ever just "appear" or "disappear" — every visual change gets a brief, smooth transition.

Empty, Error & Loading States

Every screen has at least three faces: populated, empty, and broken. AI-generated interfaces almost always show only the happy path with fake data. A polished interface acknowledges the other two.

Empty State

When a list, table, or content area has no data yet (first-time use, zero results, cleared filters):

• Center a Lucide icon (48px, neutral-300) + a short heading (Heading 3) + one line of body text (neutral-500) vertically in the content area
• Optionally include a primary action button below the text (e.g., "Create your first project")
• Do NOT show an empty table with headers and no rows — that looks like a bug, not a feature
• Do NOT use illustrations or complex graphics. Keep it text + icon. Minimal.

Error State

When something goes wrong (network failure, permission denied, server error):

• Same centered layout as empty state, but use error-500 for the icon color
• Icon: contextual — WifiOff for network errors, ShieldX for permission, AlertTriangle as a generic fallback
• Heading: brief, human-readable ("Something went wrong", "Couldn't load projects")
• Body: one sentence explaining what to do ("Check your connection and try again")
• Include a "Retry" button (secondary variant) when the action is retryable

Loading State

When content is being fetched:

• For initial page loads: Show a single centered spinner (Loader2 icon with animate-spin, 24px, neutral-400). No skeleton screens unless explicitly requested — they add complexity without clarifying the design
• For inline updates (e.g., submitting a form, loading more items): Swap the trigger button's label to a spinner + "Loading…" and disable the button
• For pull-to-refresh or lazy loading: A small spinner at the top or bottom of the list, neutral-400

The anti-pattern rule "No animated skeletons or shimmer effects in static mockups" still stands — but a simple animate-spin on a loader icon is fine for interactive interfaces.

Form Validation & Error Feedback

Inputs need to clearly communicate when something is wrong. This applies to both web and mobile. For code examples, see the Form Validation States section in references/components.md.

Behavioral Rules

• Validate on blur (when the user leaves the field), not on every keystroke — keystroke validation feels aggressive
• Show errors inline, directly below the relevant field. Never collect errors at the top of the form — users shouldn't have to hunt
• When the user corrects the input and the field is valid, remove the error state immediately (on change, not on blur)
• If the form is submitted with errors, scroll to the first invalid field and focus it

Success Confirmation (Post-Submit)

After a successful form submission, provide clear feedback. Don't just silently navigate away:

• Option A: Toast notification confirming the action + navigate to the next logical screen
• Option B: Inline success message replacing the form content (useful for single-purpose screens like "Reset password")

Toast Notifications

Transient feedback messages that confirm actions, surface errors, or provide information. Use shadcn's Sonner toast component. For code examples and the full variant table, see the Toast Notification section in references/components.md.

Positioning & Behavior

• Web: Bottom-right corner, 16px from the edge
• Mobile: Top-center, below the status bar / top bar area
• Duration: 4000ms default, 6000ms for messages with an action link. Error toasts should persist until dismissed
• Stacking: Max 3 visible at once. New toasts push older ones up (web) or down (mobile)
• Animation: Slide in from the edge + fade. Slide out + fade on dismiss. Should feel like the Transitions & Animations section — smooth, never instant

Data Visualization Palette

When rendering charts (Recharts, Chart.js, etc.), use this ordered color sequence so data visualizations feel native to the brand. The palette starts with the brand purple and fans out through distinguishable hues:

Rules

• For single-metric charts (one bar, one line, one donut), always use Brand (#5900FF)
• For two-series comparisons, use Brand + Teal
• Apply colors in order — don't skip or shuffle. Consistency across charts makes dashboards feel cohesive
• Use 10% opacity fills for area charts (e.g., #5900FF1A for brand area fill)
• Gridlines: neutral-200. Axis labels: neutral-500, caption size (12px). Axis lines: neutral-300
• Tooltips: White bg, shadow-md, rounded-md, neutral-200 border — same treatment as popovers
• Never use brand purple for "negative" or "declining" values — use Rose for that. Purple is always neutral-to-positive

Dark Mode

Dark mode is off by default. Only implement it when explicitly requested by the user or client. When dark mode is requested, follow these rules — do NOT improvise an inverted palette.

How It Works

The theme file (references/theme.css) includes a .dark class block that overrides CSS custom properties. Adding class="dark" to <html> or a wrapper element flips the entire color system without changing any component code. The neutral scale inverts so existing utilities (text-neutral-900, bg-neutral-50, border-neutral-200) automatically produce the correct dark-mode values.

Token Behavior in Dark Mode

You don't change token names in your code — the .dark override changes the values behind them. Here's what each token resolves to:

bg-white vs bg-neutral-0 — Critical Distinction

Tailwind's built-in white and black are NOT overridden in dark mode. They always resolve to literal #FFFFFF and #000000.

• Use text-white when you mean actual white — e.g., button text on a brand-500 background. This stays white in both modes. ✅
• Use bg-neutral-0 (not bg-white) for surfaces that should invert in dark mode — e.g., card backgrounds, sidebars, top bars. bg-neutral-0 maps to #FFFFFF in light and #0A0A0A in dark. ✅
• Use bg-neutral-50 for page backgrounds. Maps to #FAFAFA in light, #171717 in dark. ✅

If you use bg-white on a card, it will stay bright white in dark mode — blinding. Use bg-neutral-0 instead.

Shadows in Dark Mode

Shadows are nearly invisible on dark surfaces. The .dark block increases shadow opacity so elevation is still perceptible, but cards should primarily rely on their neutral-200 border (which maps to a subtle dark gray divider in dark mode) for definition.

Logo

Use assets/logo-mono-white.svg — the only variant approved for dark surfaces.

What NOT to Do in Dark Mode

• Do NOT manually set dark colors in component code — rely on the .dark class override
• Do NOT use bg-white for surfaces — use bg-neutral-0 so they invert properly
• Do NOT use brand-500 for large tinted surfaces — use brand-50 (which maps to a dark purple in dark mode)
• Do NOT change spacing, radius, or typography — the spatial system is mode-independent

Anti-Patterns (Do NOT)

• No gradients on buttons. Flat solid colors only.
• No colored page backgrounds. Background is always neutral-50 or neutral-0.
• No heavy borders. Max 1px for structural borders. Never 2px+.
• No rounded-full on cards. Cards are rounded-lg (10px), never circles.
• No custom fonts. DM Sans / sans-serif only. Monospace for code.
• Prefer icon + label navigation on desktop. Icon-only sidebars are acceptable if a tooltip with the label appears on hover or focus.
• No dark mode unless explicitly requested. Default is always light.
• No animated skeletons or shimmer effects in static mockups.
• No drop shadows on text. Ever.
• No border-radius mixing. Don't use the same radius token at different hierarchy levels — e.g., rounded-lg cards should contain rounded-sm children, not rounded-lg children. The inner radius should always be smaller than the outer.
• No floating labels or placeholder-as-label. Labels must always be visible above inputs. Placeholders are hints, not labels — they vanish on focus and users lose context.
• No emojis in the UI. Icons only. The only exception is user-generated content — if a user typed an emoji, display it. But never add emojis to labels, headings, buttons, nav items, placeholders, or any system-generated text.

Checklist Before Output

Before delivering any UI code, verify:

• Uses DM Sans font family (with sans-serif fallback)
• Brand purple only on interactive/active elements
• Cards have bg-neutral-0 + neutral-200 border + rounded-lg + shadow-sm
• No unauthorized colors, fonts, or shadows
• All icons from Lucide React
• shadcn components used where available (not custom recreations)
• Spacing feels generous — nothing cramped
• Page background is neutral-50, not white
• Empty states are handled (not just the happy path with fake data)
• Form inputs show error styling on validation failure (red border + message below)
• Actions provide feedback via toast or inline confirmation
• Charts (if present) use the data visualization palette in order
• All form inputs have visible external labels (not inside the input)
• Placeholder text is de-emphasized (neutral-400, normal weight)
• Casper Studios logo uses the correct variant for the background (default on light, mono-white on dark)
• If dark mode was requested: .dark class applied, logo uses mono-white variant, surfaces use bg-neutral-0 (not bg-white)
• Border-radius: buttons/inputs use rounded-md (8px), cards use rounded-lg (10px), nav items/inner elements use rounded-sm (6px)
• Button/input heights: 48px (h-12) by default, 36px (h-9) when inside cards, panels, tables, or other compact containers

Additional checks for Web Applications:

• Sidebar follows the 240px / grouped nav / active state pattern
• Responsive: works at 1280px, 768px, and 375px

Additional checks for Mobile Applications:

• Rendered inside iPhone 16 device frame (393×852, 40px outer radius, 8px bezel)
• Primary action button is pinned to bottom with safe area padding
• Navigation uses bottom tab bar, not sidebar
• Buttons and inputs are 48px height (same as global default — no mobile override needed)
• Most tap targets are 44×44px or larger (smaller is OK in dense UI, but not the default)
• Single-column layout only — no multi-column grids
• Typography uses mobile scale (H1: 24px, H2: 18px)