# margin-block

> Applies `margin-block`.

```ts
import { mb } from "@sdxc/u/size";
```

Applies `margin-block`. One value applies both block edges; two values
map to block-start then block-end.

## Quick reference

Every documented call, beside the CSS it emits.

| Call | CSS |
| --- | --- |
| `u.mb(4)` | `css({ marginBlock: "calc(var(--ui-spacing, 0.25rem) * 4)" })` |

## Examples

### Basic example

Use `mb(n)` to add margin to the block-start and block-end edges of an element, above and below it in horizontal text:

```tsx
<div mix={[...]}>
	<div mix={[mb(8), ...]}>mb(8)</div>
</div>
```

### Start and end

Pass two values to set the block-start and then the block-end margin, like `mb(2, 10)`:

```tsx
<div mix={[...]}>
	<div mix={[mb(2, 10), ...]}>mb(2, 10)</div>
</div>
```

## Using a custom value

Every scale argument also takes a raw CSS value, which passes through untouched.

```ts
u.mb("2.75rem")
```

## Applying on a state

Wrap the call in a state utility to scope it to one selector.

```ts
u.hover(u.mb(4))
```

## Responsive design

Wrap the call in a container query to scope it to one width.

```ts
u.at("md", u.mb(4))
```

## Customizing your theme

### Customizing spacing

Every numeric step multiplies `--ui-spacing`, so redefining it rescales every spacing and sizing utility at once:

```css
:root {
	--ui-spacing: 0.25rem;
}
```

Every call that names the step now reads the new value:

```ts
mb(4)
```

## Signature

```ts
u.mb(...values: SpacingValue[])
```