# A theme for light terminals

> Declare the background your users read on, let roundel pick the brand shade that reads on it, and check the result before it ships.

Source: https://roundel.interlace.tools/docs/recipes/light-terminals

The default ground is near-black. On a light terminal, say so, and every hex token is checked —
and the default brand tokens chosen — against white instead:

```js title="light-check.mjs"
import { reportTheme } from 'roundel/contrast';
import { audit } from 'roundel/theme';

const theme = { ground: '#fdfdfd', warn: '#9a6700' };
console.log(reportTheme(audit(theme)));
```

```text title="node light-check.mjs"
pass  error  truecolor  #a84c17 on #fdfdfd  5.56:1 (needs 4.5:1)
pass  error  256        #af5f00 on #fdfdfd  4.63:1 (needs 4.5:1)
pass  warn   truecolor  #9a6700 on #fdfdfd  4.79:1 (needs 4.5:1)
pass  warn   256        #af5f00 on #fdfdfd  4.63:1 (needs 4.5:1)
pass  ok     truecolor  #0a6b47 on #fdfdfd  6.44:1 (needs 4.5:1)
pass  ok     256        #005f5f on #fdfdfd  7.37:1 (needs 4.5:1)
```

`error` and `ok` were not given, so they are the brand's deep shades, the ones that read on a
light ground. `warn` was given as a hex, so it is checked too; the default `yellow` would not
have been, because a format name is the user's own palette.

There is no way to ask a terminal what its background is, so the choice is yours. A program
that serves both can read a setting of its own and fly the matching theme; the check runs on
whichever it flies.