App Design

Your job is to build cohesive, distinctive apps — not just correct ones. Add character through intentional design decisions — typography pairing, color emphasis, spatial rhythm, and a clear visual point of view.

Aesthetic Direction

Before building anything, decide the app's tone in one word and its signature detail — the one thing someone notices first. These two choices guide every decision that follows. Pick a tone that is specific and bold, not safe or generic. Examples like editorial, geometric, organic, industrial, playful, or minimal are starting points — don't limit yourself to these. Invent a direction that fits the app's purpose.

Then match your execution to your direction — a maximalist direction needs layered effects and rich detail in the code; a minimalist direction needs precise spacing, restraint, and careful typography. Elegance comes from committing to the direction fully, not from adding more.

Typography

Pick fonts that set the app's character — this is one of the strongest signals of intentional design. At minimum choose a characterful --font-heading paired with a complementary --font-base, ideally from the same foundry or design family. Update --font-monospace and --font-numeric if necessary. Avoid generic defaults like Arial, Inter, or Roboto.

Load fonts via Google Fonts (or another CDN) as <link> tags in index.html, then update the font family tokens in the @theme block of global.css.

Theming Workflow

Start by customizing src/global.css — this is the single source of truth for the app's active visual identity. Every component uses these tokens, so setting them first means the entire UI shifts together.

1. Colors: Update the semantic color tokens (--color-primary, --color-background, --color-card, --color-border, etc.) in both the @theme block and the .dark override to match the aesthetic direction. The defaults are neutral blue/grey — make them yours.
2. Data palette: Define the ten data color tokens (--color-data-1–--color-data-10) as the active palette, with .dark overrides, per the data color rules. Then populate src/data-palette-presets.json with three alternative palettes — never a copy of the active one — each with a kebab-case id, a concise name, and colors.light / colors.dark arrays of exactly ten six-digit hex colors in token order.
3. Radius: Adjust --radius (the base radius) and the radius scale to match the tone — sharp/geometric (lower values), soft/rounded (higher values), or pill-shaped (--radius-full).
4. Fonts: Update the font family tokens as described in the Typography section above.
5. Then build components. Focus component-level styling on layout, spacing, and element-specific details — not re-specifying colors and radii that the tokens already handle.
6. Selective overrides last. After the base theme is in place, inspect and adjust individual components that need to deviate — an accent-colored card border, a button with a unique hover effect, etc.

Keep these principles in mind:

• Use semantic color tokens so surfaces, text, and borders adapt correctly to light and dark mode.
• Maintain sufficient contrast between text and backgrounds.
• The recommended minimum text size is text-200.
• Keep spacing consistent — use the spacing tokens from the theme rather than arbitrary values.
• Ensure all interactive elements are keyboard-accessible with visible focus indicators and appropriate disabled states.

Read these reference files — they include "Make it yours" prompts that tie back to the aesthetic direction above:

• UI Style Recipes — per-element styling guidance for buttons, cards, inputs, dialogs, tabs, tooltips, tables, and more.
• Visual Style Recipes — chart theming, Vega-Lite config, dark mode chart support, and mark-specific styling.

App Layout

These are good defaults for app structure. Adapt them to the specific app's needs.

Page Structure

• The app layout should fill the viewport.
• On wide screens, constrain the content width so it doesn't stretch uncomfortably. Use responsive breakpoints or multi-column layouts to make good use of available space.

Don't default to the same layout every time. The structure should serve the aesthetic direction — a sidebar + main content split, a full-width single column, a multi-panel master-detail, an asymmetric split, or something else entirely. These are starting points, not an exhaustive list. Invent a layout that fits the app's purpose and tone.

The header/toolbar is part of the design language — not every app needs a traditional fixed header. Consider alternatives: a floating command bar, a compact inline toolbar, a branded banner, a collapsible drawer, a minimal top-right action cluster, or no header at all if the content speaks for itself.

Container Sizing

VegaVisual and other content components fill their container — the container controls their dimensions. Without constraints, charts and content stretch to the full viewport width, which produces squished, unreadable visuals on wide screens.

• Constrain the dashboard wrapper, not individual charts. Apply a max-width to the outermost content wrapper that holds the dashboard. This single constraint keeps the entire layout proportional on wide monitors. If the app lacks an outer wrapper, create one.
• Do not constrain individual chart containers. Let the wrapper width plus grid columns determine each chart's size naturally.
• If the user explicitly requests full-width charts, confirm the design choice before proceeding.

Dashboard Grid

• Start mobile-first and scale up columns with responsive breakpoints.
• Support mixed-size cards via span utilities.

Avoid uniform grids where every card is the same size — they look like a spreadsheet. Vary card spans to create visual hierarchy: a wide chart spanning two columns next to a tall narrow KPI panel, or a full-width table below a row of smaller cards. Let the data importance guide which elements get more space.

Loading, Empty & Error States

Every component that depends on async data should handle all three states:

Dark Mode

Include a light/dark mode toggle in the app header or toolbar. Use the useAppTheme hook from @/hooks/use-theme to read and toggle the theme.

Coding Conventions

• Styling: Tailwind CSS v4 utility classes for all styling. Theme colors are defined as CSS custom properties in src/global.css using @theme. Use Tailwind classes directly in JSX.
• Theming: Light/dark color tokens defined in src/global.css via CSS custom properties. Dark mode uses the .dark class on the root html element, auto-detected via prefers-color-scheme, data-appearance attribute, or .dark class. The useAppTheme hook in src/hooks/use-theme.ts manages the toggle.
• CSS class merging: Use cn() from @/lib/utils (powered by clsx + tailwind-merge) to conditionally combine Tailwind class names.
• Icons: Lucide React for UI icons.
• UI Components: Use Radix primitives with Tailwind CSS styling for all interactive elements — buttons, inputs, dialogs, menus, tabs, etc.

UI Token Rules

All styling must use the design tokens defined in src/global.css via Tailwind utility classes. Never hardcode raw color values, pixel sizes, or font stacks — raw values are only permitted in global.css and src/data-palette-presets.json. Refer to global.css for available tokens, their values, and expected usage.

Examples:

• bg-primary text-primary-foreground — not bg-blue-600 text-white
• text-300 — not text-sm or text-[14px]
• p-400 gap-300 — not p-4 or gap-3
• font-semibold — not font-[600]
• rounded-xl — not rounded-[8px]
• icon-size-200 — not w-4 h-4

cn() and tailwind-merge conflicts: tailwind-merge treats text-* utilities as one conflict group. In cn(), combining text size and text color with ambiguous text-* classes can drop one class. Prefer explicit length syntax for font size (e.g., text-[length:var(--text-300)]) when combining with text color classes inside cn(). If classes are static and not merged, text-300 text-foreground is acceptable.

Form element font inheritance: Native form controls may not inherit the page font family by default. Ensure base styles in global.css set font-family: inherit for select, input, textarea, and button.

Final Audit

After assembling a layout, audit each element in its actual context — not in isolation. A component may look correct on its own but break the visual rhythm of the page. Check: Is every text legible? Are labels proportional to their controls? Are toolbar rows aligned on a shared edge? Do charts fill their containers? Do repeated elements (badges in tables, icons in lists) maintain appropriate visual weight for their density? Fix anything that fails.