# Local Cal Design System Inspired by Vercel

## 0. Product Interpretation

This document is not a brief for a Vercel-style marketing homepage. It defines how Vercel's visual language should be adapted to `local-cal`, a utility-first calendar product.

The approved product direction is an `event-first product console with co-equal AI capture`.

### Core Product Rules
- Keep the app single-page, but lightly restructure hierarchy.
- Desktop/tablet: AI capture and timeline begin on the same top row and the same vertical start line.
- Desktop/tablet: the timeline remains the dominant surface through width, depth, and content mass, not by appearing earlier in the layout.
- Mobile: prioritize `AI capture -> timeline scan -> export`.
- Mobile: do not create a separate review flow; review happens by scanning the timeline.
- Text input and file attachments are equally important in the AI capture section.
- Manual event creation is a secondary power-user path and should live behind a quieter `More` or secondary menu.
- Validation problems must appear inline under affected events in the timeline, not only in forms.

### Product Stance
- Utility-first, not editorial-first
- Event-first on desktop/tablet
- Capture-first in the first mobile viewport
- Vercel-inspired, but adapted for a working app rather than a product showcase

## 1. Visual Theme & Atmosphere

Vercel's website is the visual thesis of developer infrastructure made invisible — a design system so restrained it borders on philosophical. For `local-cal`, that same restraint should be applied to a dense, working interface rather than a marketing narrative. The app should be overwhelmingly white (`#ffffff`) with near-black (`#171717`) text in light mode, creating a precise product-console feel where every element earns its pixel. Light mode is the default and canonical expression of the system. This isn't minimalism as decoration; it's minimalism as engineering principle.

The custom Geist font family is the crown jewel. Geist Sans uses aggressive negative letter-spacing (-2.4px to -2.88px at display sizes), creating headlines that feel compressed, urgent, and engineered — like code that's been minified for production. At body sizes, the tracking relaxes but the geometric precision persists. Geist Mono completes the system as the monospace companion for code, terminal output, and technical labels. Both fonts enable OpenType `"liga"` (ligatures) globally, adding a layer of typographic sophistication that rewards close reading.

What distinguishes Vercel from other monochrome design systems is its shadow-as-border philosophy. Instead of traditional CSS borders, Vercel uses `box-shadow: 0px 0px 0px 1px rgba(0,0,0,0.08)` — a zero-offset, zero-blur, 1px-spread shadow that creates a border-like line without the box model implications. This technique allows borders to exist in the shadow layer, enabling smoother transitions, rounded corners without clipping, and a subtler visual weight than traditional borders. The entire depth system is built on layered, multi-value shadow stacks where each layer serves a specific purpose: one for the border, one for soft elevation, one for ambient depth.

Dark mode is not a separate aesthetic direction and not a generic charcoal inversion. It is a token-level adaptation of the same product-console system: the same hierarchy, the same spacing, the same shadow architecture, and the same restraint. Dark surfaces should remain distinct from the page through whisper-light white border shadows, low-contrast interior glow, and controlled neutral separation rather than black cutouts or heavy elevation.

**Key Characteristics:**
- Geist Sans with extreme negative letter-spacing (-2.4px to -2.88px at display) — text as compressed infrastructure
- Geist Mono for code and technical labels with OpenType `"liga"` globally
- Shadow-as-border technique: `box-shadow 0px 0px 0px 1px` replaces traditional borders throughout
- Multi-layer shadow stacks for nuanced depth (border + elevation + ambient in single declarations)
- Near-pure white canvas with `#171717` text — not quite black, creating micro-contrast softness
- Light mode is the default product presentation; dark mode is a faithful adaptation, not a re-theme
- Functional accent colors used only for real event state and utilities, never decorative workflow chrome
- Focus ring system using `hsla(212, 100%, 48%, 1)` — a saturated blue for accessibility
- Pill badges (9999px) with tinted backgrounds for status indicators

## 2. Color Palette & Roles

### Primary
- **Vercel Black** (`#171717`): Primary text, headings, dark surface backgrounds. Not pure black — the slight warmth prevents harshness.
- **Pure White** (`#ffffff`): Page background, card surfaces, button text on dark.
- **True Black** (`#000000`): Secondary use, `--geist-console-text-color-default`, used in specific console/code contexts.

### Dark Theme Neutrals
- **Dark Canvas** (`#121212`): Dark page background. Use for the app shell only, never as a default theme.
- **Dark Surface** (`#181818`): Primary dark cards, dialogs, menus, and nav surfaces.
- **Dark Secondary Surface** (`#1d1d1d`): Inputs, action bars, and quieter tool surfaces in dark mode.
- **Dark Subtle Surface** (`#202020`): Hover, active, and accent-neutral dark states.
- **Dark Muted Text** (`#a3a3a3`): Secondary copy in dark mode.

### Functional Accent Colors
- **Action Blue** (`#0a72ef`): Use for active utility cues, attachment affordances, and recurrence emphasis when blue is semantically useful.
- **Signal Pink** (`#de1d8d`): Use sparingly for metadata emphasis such as link state or secondary scan cues when pink improves hierarchy.
- **Warning Red** (`#ff5b4f`): Use for validation problems, destructive intent, and inline event warnings.

### Console / Code Colors
- **Console Blue** (`#0070f3`): `--geist-console-text-color-blue`, syntax highlighting blue.
- **Console Purple** (`#7928ca`): `--geist-console-text-color-purple`, syntax highlighting purple.
- **Console Pink** (`#eb367f`): `--geist-console-text-color-pink`, syntax highlighting pink.

### Interactive
- **Link Blue** (`#0072f5`): Primary link color with underline decoration.
- **Focus Blue** (`hsla(212, 100%, 48%, 1)`): `--ds-focus-color`, focus ring on interactive elements.
- **Ring Blue** (`rgba(147, 197, 253, 0.5)`): `--tw-ring-color`, Tailwind ring utility.

### Neutral Scale
- **Gray 900** (`#171717`): Primary text, headings, nav text.
- **Gray 600** (`#4d4d4d`): Secondary text, description copy.
- **Gray 500** (`#666666`): Tertiary text, muted links.
- **Gray 400** (`#808080`): Placeholder text, disabled states.
- **Gray 100** (`#ebebeb`): Borders, card outlines, dividers.
- **Gray 50** (`#fafafa`): Subtle surface tint, inner shadow highlight.

### Surface & Overlay
- **Overlay Backdrop** (`hsla(0, 0%, 98%, 1)`): `--ds-overlay-backdrop-color`, modal/dialog backdrop.
- **Selection Text** (`hsla(0, 0%, 95%, 1)`): `--geist-selection-text-color`, text selection highlight.
- **Badge Blue Bg** (`#ebf5ff`): Pill badge background, tinted blue surface.
- **Badge Blue Text** (`#0068d6`): Pill badge text, darker blue for readability.

### Shadows & Depth
- **Border Shadow** (`rgba(0, 0, 0, 0.08) 0px 0px 0px 1px`): The signature — replaces traditional borders.
- **Subtle Elevation** (`rgba(0, 0, 0, 0.04) 0px 2px 2px`): Minimal lift for cards.
- **Card Stack** (`rgba(0,0,0,0.08) 0px 0px 0px 1px, rgba(0,0,0,0.04) 0px 2px 2px, rgba(0,0,0,0.04) 0px 8px 8px -8px, #fafafa 0px 0px 0px 1px`): Full multi-layer card shadow.
- **Ring Border** (`rgb(235, 235, 235) 0px 0px 0px 1px`): Light gray ring-border for tabs and images.
- **Dark Border Shadow** (`rgba(255, 255, 255, 0.08) 0px 0px 0px 1px`): Dark-mode border layer. Use this instead of reusing the light border shadow on dark surfaces.
- **Dark Card Stack** (`rgba(255,255,255,0.08) 0px 0px 0px 1px, rgba(0,0,0,0.20) 0px 2px 2px, rgba(0,0,0,0.28) 0px 8px 8px -8px, rgba(255,255,255,0.03) 0px 0px 0px 1px`): Dark-mode equivalent of the light card stack.

## 3. Typography Rules

### Font Family
- **Primary**: `Geist`, with fallbacks: `Arial, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol`
- **Monospace**: `Geist Mono`, with fallbacks: `ui-monospace, SFMono-Regular, Roboto Mono, Menlo, Monaco, Liberation Mono, DejaVu Sans Mono, Courier New`
- **OpenType Features**: `"liga"` enabled globally on all Geist text; `"tnum"` for tabular numbers on specific captions.

### Hierarchy

| Role | Font | Size | Weight | Line Height | Letter Spacing | Notes |
|------|------|------|--------|-------------|----------------|-------|
| Display Hero | Geist | 48px (3.00rem) | 600 | 1.00–1.17 (tight) | -2.4px to -2.88px | Maximum compression, billboard impact |
| Section Heading | Geist | 40px (2.50rem) | 600 | 1.20 (tight) | -2.4px | Feature section titles |
| Sub-heading Large | Geist | 32px (2.00rem) | 600 | 1.25 (tight) | -1.28px | Card headings, sub-sections |
| Sub-heading | Geist | 32px (2.00rem) | 400 | 1.50 | -1.28px | Lighter sub-headings |
| Card Title | Geist | 24px (1.50rem) | 600 | 1.33 | -0.96px | Feature cards |
| Card Title Light | Geist | 24px (1.50rem) | 500 | 1.33 | -0.96px | Secondary card headings |
| Body Large | Geist | 20px (1.25rem) | 400 | 1.80 (relaxed) | normal | Introductions, feature descriptions |
| Body | Geist | 18px (1.13rem) | 400 | 1.56 | normal | Standard reading text |
| Body Small | Geist | 16px (1.00rem) | 400 | 1.50 | normal | Standard UI text |
| Body Medium | Geist | 16px (1.00rem) | 500 | 1.50 | normal | Navigation, emphasized text |
| Body Semibold | Geist | 16px (1.00rem) | 600 | 1.50 | -0.32px | Strong labels, active states |
| Button / Link | Geist | 14px (0.88rem) | 500 | 1.43 | normal | Buttons, links, captions |
| Button Small | Geist | 14px (0.88rem) | 400 | 1.00 (tight) | normal | Compact buttons |
| Caption | Geist | 12px (0.75rem) | 400–500 | 1.33 | normal | Metadata, tags |
| Mono Body | Geist Mono | 16px (1.00rem) | 400 | 1.50 | normal | Code blocks |
| Mono Caption | Geist Mono | 13px (0.81rem) | 500 | 1.54 | normal | Code labels |
| Mono Small | Geist Mono | 12px (0.75rem) | 500 | 1.00 (tight) | normal | `text-transform: uppercase`, technical labels |
| Micro Badge | Geist | 7px (0.44rem) | 700 | 1.00 (tight) | normal | `text-transform: uppercase`, tiny badges |

### Principles
- **Compression as identity**: Geist Sans at display sizes uses -2.4px to -2.88px letter-spacing — the most aggressive negative tracking of any major design system. This creates text that feels _minified_, like code optimized for production. The tracking progressively relaxes as size decreases: -1.28px at 32px, -0.96px at 24px, -0.32px at 16px, and normal at 14px.
- **Ligatures everywhere**: Every Geist text element enables OpenType `"liga"`. Ligatures aren't decorative — they're structural, creating tighter, more efficient glyph combinations.
- **Three weights, strict roles**: 400 (body/reading), 500 (UI/interactive), 600 (headings/emphasis). No bold (700) except for tiny micro-badges. This narrow weight range creates hierarchy through size and tracking, not weight.
- **Mono for identity**: Geist Mono in uppercase with `"tnum"` or `"liga"` serves as the "developer console" voice — compact technical labels that connect the marketing site to the product.

## 4. Component Stylings

### Buttons

**Primary White (Shadow-bordered)**
- Background: `#ffffff`
- Text: `#171717`
- Padding: 0px 6px (minimal — content-driven width)
- Radius: 6px (subtly rounded)
- Shadow: `rgb(235, 235, 235) 0px 0px 0px 1px` (ring-border)
- Hover: background shifts to `var(--ds-gray-1000)` (dark)
- Focus: `2px solid var(--ds-focus-color)` outline + `var(--ds-focus-ring)` shadow
- Use: Standard secondary button

**Primary Dark (Inferred from Geist system)**
- Background: `#171717`
- Text: `#ffffff`
- Padding: 8px 16px
- Radius: 6px
- Use: Primary CTA ("Start Deploying", "Get Started")

**Pill Button / Badge**
- Background: `#ebf5ff` (tinted blue)
- Text: `#0068d6`
- Padding: 0px 10px
- Radius: 9999px (full pill)
- Font: 12px weight 500
- Use: Status badges, tags, feature labels

**Large Pill (Navigation)**
- Background: transparent or `#171717`
- Radius: 64px–100px
- Use: Tab navigation, section selectors

### Cards & Containers
- Background: `#ffffff`
- Border: via shadow — `rgba(0, 0, 0, 0.08) 0px 0px 0px 1px`
- Radius: 8px (standard), 12px (featured/image cards)
- Shadow stack: `rgba(0,0,0,0.08) 0px 0px 0px 1px, rgba(0,0,0,0.04) 0px 2px 2px, #fafafa 0px 0px 0px 1px`
- Image cards: `1px solid #ebebeb` with 12px top radius
- Hover: subtle shadow intensification

### Inputs & Forms
- Radio: standard styling with focus `var(--ds-gray-200)` background
- Focus shadow: `1px 0 0 0 var(--ds-gray-alpha-600)`
- Focus outline: `2px solid var(--ds-focus-color)` — consistent blue focus ring
- Border: via shadow technique, not traditional border
- In dark mode, inputs and textareas sit on a quieter secondary surface rather than appearing as black voids carved out of the card

### Navigation
- Clean horizontal nav on white, sticky
- Vercel logotype left-aligned, 262x52px
- Links: Geist 14px weight 500, `#171717` text
- Active: weight 600 or underline
- CTA: dark pill buttons ("Start Deploying", "Contact Sales")
- Mobile: hamburger menu collapse
- Product dropdowns with multi-level menus

### Image Treatment
- Product screenshots with `1px solid #ebebeb` border
- Top-rounded images: `12px 12px 0px 0px` radius
- Dashboard/code preview screenshots dominate feature sections
- Soft gradient backgrounds behind hero images (pastel multi-color)

### Distinctive Components

**AI Capture Surface**
- A primary product section, not an accessory toolbar
- Text input and file attachments have equal visual importance
- On desktop, it lives beside the timeline with aligned top edges
- On mobile, it becomes the first major surface in the viewport

**Event Timeline**
- The dominant product surface on desktop/tablet
- Cards optimized for quick scanning of title, time, recurrence, links, and problem states
- Review happens by visually scanning the timeline, not by stepping through a separate review stage
- Validation warnings can appear inline below affected event cards

**Trust Bar / Logo Grid**
- Company logos (Perplexity, ChatGPT, Cursor, etc.) in grayscale
- Horizontal scroll or grid layout
- Subtle `#ebebeb` border separation

**Metric Cards**
- Large number display (e.g., "10x faster")
- Geist 48px weight 600 for the metric
- Description below in gray body text
- Shadow-bordered card container

## 5. Layout Principles

### Spacing System
- Base unit: 8px
- Scale: 1px, 2px, 3px, 4px, 5px, 6px, 8px, 10px, 12px, 14px, 16px, 32px, 36px, 40px
- Notable gap: jumps from 16px to 32px — no 20px or 24px in primary scale

### Grid & Container
- Max content width: approximately 1200px
- Main app shell: compact infrastructure bar plus a primary two-section workspace
- Desktop/tablet workspace: AI capture and timeline aligned on the same top row
- Mobile workspace: AI capture first, timeline immediately after, export easy to reach
- Full-width dividers using `border-bottom: 1px solid #171717`
- Cards and tool surfaces can be full-width or contained with shadow-border treatment

### Whitespace Philosophy
- **Balanced precision**: Preserve generous whitespace, but do not let the app drift into gallery-like pacing that slows frequent actions.
- **Compressed text, usable space**: Headlines can stay dense and compressed while cards, forms, and timelines remain operationally efficient.
- **Section rhythm**: Separate zones through spacing, surface treatment, and hierarchy, not through loud color blocking.

### Border Radius Scale
- Micro (2px): Inline code snippets, small spans
- Subtle (4px): Small containers
- Standard (6px): Buttons, links, functional elements
- Comfortable (8px): Cards, list items
- Image (12px): Featured cards, image containers (top-rounded)
- Large (64px): Tab navigation pills
- XL (100px): Large navigation links
- Full Pill (9999px): Badges, status pills, tags
- Circle (50%): Menu toggle, avatar containers

## 6. Depth & Elevation

| Level | Treatment | Use |
|-------|-----------|-----|
| Flat (Level 0) | No shadow | Page background, text blocks |
| Ring (Level 1) | `rgba(0,0,0,0.08) 0px 0px 0px 1px` | Shadow-as-border for most elements |
| Light Ring (Level 1b) | `rgb(235,235,235) 0px 0px 0px 1px` | Lighter ring for tabs, images |
| Dark Ring (Level 1c) | `rgba(255,255,255,0.08) 0px 0px 0px 1px` | Shadow-as-border for dark surfaces |
| Subtle Card (Level 2) | Ring + `rgba(0,0,0,0.04) 0px 2px 2px` | Standard cards with minimal lift |
| Full Card (Level 3) | Ring + Subtle + `rgba(0,0,0,0.04) 0px 8px 8px -8px` + inner light-mode glow | Featured cards, highlighted panels |
| Full Card Dark (Level 3d) | Dark Ring + `rgba(0,0,0,0.20) 0px 2px 2px` + `rgba(0,0,0,0.28) 0px 8px 8px -8px` + inner `rgba(255,255,255,0.03)` glow | Featured dark cards, dialogs, menus |
| Focus (Accessibility) | `2px solid hsla(212, 100%, 48%, 1)` outline | Keyboard focus on all interactive elements |

**Shadow Philosophy**: Vercel has arguably the most sophisticated shadow system in modern web design. Rather than using shadows for elevation in the traditional Material Design sense, Vercel uses multi-value shadow stacks where each layer has a distinct architectural purpose: one creates the "border" (0px spread, 1px), another adds ambient softness (2px blur), another handles depth at distance (8px blur with negative spread), and an inner ring creates the subtle highlight that makes the card "glow" from within. In light mode that inner ring is `#fafafa`; in dark mode it becomes a restrained low-alpha white. This layered approach means cards feel built, not floating.

### Decorative Depth
- Decorative gradients should be minimal to nonexistent in the core app shell
- Section borders: use only where structure benefits from them; default to shadow-border separation first
- No loud background color variation — depth comes primarily from shadow layering and border contrast

## 7. Do's and Don'ts

### Do
- Use Geist Sans with aggressive negative letter-spacing at display sizes (-2.4px to -2.88px at 48px)
- Use shadow-as-border (`0px 0px 0px 1px rgba(0,0,0,0.08)`) instead of traditional CSS borders
- Enable `"liga"` on all Geist text — ligatures are structural, not optional
- Use the three-weight system: 400 (body), 500 (UI), 600 (headings)
- Apply accent colors only to real event state, utility emphasis, link state, recurrence, or validation
- Use multi-layer shadow stacks for cards (border + elevation + ambient + inner highlight)
- Keep the color palette achromatic — grays from `#171717` to `#ffffff` are the system
- Use `#171717` instead of `#000000` for primary text — the micro-warmth matters
- Keep dark mode on the same system by swapping tokens, not by inventing a second visual language
- Keep AI capture attachments as visually important as typed input
- Surface validation issues inline on timeline cards when event data is invalid

### Don't
- Don't use positive letter-spacing on Geist Sans — it's always negative or zero
- Don't use weight 700 (bold) on body text — 600 is the maximum, used only for headings
- Don't use traditional CSS `border` on cards — use the shadow-border technique
- Don't introduce warm colors (oranges, yellows, greens) into the UI chrome
- Don't add `Develop / Preview / Ship` tags or section metaphors to the app shell or event cards
- Don't apply accent colors decoratively or as marketing-style workflow chrome
- Don't use heavy shadows (> 0.1 opacity) — the shadow system is whisper-level
- Don't increase body text letter-spacing — Geist is designed to run tight
- Don't use pill radius (9999px) on primary action buttons — pills are for badges/tags only
- Don't reuse the light-mode `#fafafa` inner ring on dark surfaces; use the dark equivalent low-alpha white glow instead
- Don't make dark mode a generic black inversion with undifferentiated cards, menus, and inputs

## 8. Responsive Behavior

### Breakpoints
| Name | Width | Key Changes |
|------|-------|-------------|
| Mobile Small | <400px | Tight single column, minimal padding |
| Mobile | 400–600px | Standard mobile, stacked layout |
| Tablet Small | 600–768px | 2-column grids begin |
| Tablet | 768–1024px | Full card grids, expanded padding |
| Desktop Small | 1024–1200px | Standard desktop layout |
| Desktop | 1200–1400px | Full layout, maximum content width |
| Large Desktop | >1400px | Centered, generous margins |

### Touch Targets
- Buttons use comfortable padding (8px–16px vertical)
- Navigation links at 14px with adequate spacing
- Pill badges have 10px horizontal padding for tap targets
- Mobile menu toggle uses 50% radius circular button

### Collapsing Strategy
- Hero: display 48px → scales down, maintains negative tracking proportionally
- Top-row workspace: aligned desktop two-section layout → stacked mobile flow
- Mobile order: AI capture → timeline → export, with import/manual create demoted
- Timeline remains the main review surface at all sizes
- Attachment affordances stay prominent on mobile rather than collapsing into hidden extras
- Trust bar logos: grid → horizontal scroll
- Footer: multi-column → stacked single column
- Section spacing: reduce on mobile, but maintain clarity between AI capture and timeline

### Image Behavior
- Dashboard screenshots maintain border treatment at all sizes
- Hero gradient softens/simplifies on mobile
- Product screenshots use responsive images with consistent border radius
- Full-width sections maintain edge-to-edge treatment

## 9. Agent Prompt Guide

### Quick Color Reference
- Primary CTA: Vercel Black (`#171717`)
- Background: Pure White (`#ffffff`)
- Heading text: Vercel Black (`#171717`)
- Body text: Gray 600 (`#4d4d4d`)
- Border (shadow): `rgba(0, 0, 0, 0.08) 0px 0px 0px 1px`
- Link: Link Blue (`#0072f5`)
- Focus ring: Focus Blue (`hsla(212, 100%, 48%, 1)`)
- Dark-mode background: `#121212`; primary dark surface: `#181818`; input/tool surface: `#1d1d1d`

### Example Component Prompts
- "Create a desktop app shell with a thin infrastructure bar and a top-row two-section workspace. The AI capture section and timeline section start on the same vertical level, but the timeline has more width and deeper continuation. Use white surfaces, shadow-borders, Geist headings, and restrained metadata accents."
- "Design an AI capture panel for a utility app. Text input and file attachments must have equal visual importance. Use a white surface, shadow-border, 8px-10px radius, Geist headings, and a dark primary action."
- "Design an event card: white background, no CSS border. Use shadow stack: rgba(0,0,0,0.08) 0px 0px 0px 1px, rgba(0,0,0,0.04) 0px 2px 2px, #fafafa 0px 0px 0px 1px. Title at 24px Geist weight 600, letter-spacing -0.96px. Metadata should emphasize time, recurrence, links, and warnings instead of workflow tags."
- "Create a mobile app view where AI capture comes first, timeline follows immediately after, export stays easy to reach, and manual create is tucked into a More menu."
- "Design an inline validation warning for an event card using subtle red emphasis, shadow-border treatment, and strong readability in both light and dark themes."

### Iteration Guide
1. Always use shadow-as-border instead of CSS border — `0px 0px 0px 1px rgba(0,0,0,0.08)` is the foundation
2. Letter-spacing scales with font size: -2.4px at 48px, -1.28px at 32px, -0.96px at 24px, normal at 14px
3. Three weights only: 400 (read), 500 (interact), 600 (announce)
4. Color is functional, never decorative — accent colors mark real event state, utility emphasis, or warnings only
5. The inner glow stays theme-aware: `#fafafa` in light mode, restrained low-alpha white in dark mode
6. Geist Mono uppercase for technical labels, Geist Sans for everything else
