Styling

Customize the appearance of A2UI surfaces with CSS custom properties, fonts, and component-level overrides.

A2UI surfaces support theming through CSS custom properties scoped to the .a2ui-surface class.

Theme CSS#

Create a theme file and import it in your layout:

src/a2ui/theme.css

.a2ui-surface {
  --primary: #111111;
  --primary-foreground: #ffffff;
  --card: #ffffff;
  --border: #e0e0e0;
  --radius: 12px;
  --foreground: #111111;
  --input: #d4d4d4;
  --background: #fafafa;
}

src/app/layout.tsx

import "@/a2ui/theme.css";

CSS custom properties reference#

Variable	Default	Description
`--primary`	—	Primary accent color (buttons, links)
`--primary-foreground`	—	Text color on primary backgrounds
`--card`	—	Card background color
`--border`	—	Border color for cards, dividers, inputs
`--radius`	—	Border radius for cards and buttons
`--foreground`	—	Default text color
`--input`	—	Input field border color
`--background`	—	Surface background color

These variables are scoped to .a2ui-surface — they won't affect the rest of your app. You can also set them on :root if you want global defaults.

Custom fonts#

Override the font family on the surface container:

src/a2ui/theme.css

@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700&display=swap');

.a2ui-surface {
  font-family: "Plus Jakarta Sans", -apple-system, BlinkMacSystemFont, system-ui, sans-serif !important;
  letter-spacing: -0.01em;
}

Image sizing#

A2UI surfaces render Image components at their natural size. For consistent layouts (e.g., airline logos, avatars), constrain images with CSS:

src/a2ui/theme.css

/* Constrain logos and avatars */
.a2ui-surface img {
  max-width: 28px;
  max-height: 28px;
  border-radius: 4px;
}

/* Smaller status indicator icons */
.a2ui-surface img[alt="On Time"],
.a2ui-surface img[alt="Delayed"] {
  max-width: 10px;
  max-height: 10px;
  border-radius: 50%;
}

Card width#

When streaming cards one-by-one, a single card can collapse to a narrow width. Set a minimum:

src/a2ui/theme.css

.a2ui-surface .a2ui-card {
  min-width: 280px;
}

Dark mode#

Target dark mode with a class or media query:

src/a2ui/theme.css

.dark .a2ui-surface,
@media (prefers-color-scheme: dark) {
  .a2ui-surface {
    --primary: #e5e5e5;
    --primary-foreground: #111111;
    --card: #1a1a1a;
    --border: #333333;
    --foreground: #e5e5e5;
    --input: #444444;
    --background: #111111;
  }
}

Full example#

Here's a complete theme file combining all the patterns above:

src/a2ui/theme.css

@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700&display=swap');

.a2ui-surface {
  /* Colors */
  --primary: #111111;
  --primary-foreground: #ffffff;
  --card: #ffffff;
  --border: #e0e0e0;
  --radius: 12px;
  --foreground: #111111;
  --input: #d4d4d4;
  --background: #fafafa;

  /* Typography */
  font-family: "Plus Jakarta Sans", -apple-system, BlinkMacSystemFont, system-ui, sans-serif !important;
  letter-spacing: -0.01em;
}

/* Image constraints */
.a2ui-surface img {
  max-width: 28px;
  max-height: 28px;
  border-radius: 4px;
}

/* Streaming card width */
.a2ui-surface .a2ui-card {
  min-width: 280px;
}

Styling

Theme CSS#

CSS custom properties reference#

Custom fonts#

Image sizing#

Card width#

Dark mode#

Full example#

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