# backface-visibility

> Controls whether the back face of a 3D-transformed element renders once it rotates away from the viewer; the `"hidden"` default keeps flip-card and page-turn effects showing only their front face.

```ts
import { backfaceVisibility } from "@sdxc/u/effects";
```

Controls whether the back face of a 3D-transformed element renders once it
rotates away from the viewer; the `"hidden"` default keeps flip-card and
page-turn effects showing only their front face.

## Quick reference

Every documented call, beside the CSS it emits.

| Call | CSS |
| --- | --- |
| `u.backfaceVisibility()` | `css({ backfaceVisibility: "hidden" })` |

## Examples

### Basic example

Use `backfaceVisibility("hidden")` to hide an element once a 3D transform turns its back to the viewer, or `"visible"` to show it mirrored:

```tsx
<div mix={[perspective(600), ...]}>
	<div mix={[...]}>
		<div mix={[rotateY(150), backfaceVisibility("visible"), ...]}>visible</div>
	</div>
	<div mix={[...]}>
		<div mix={[rotateY(150), backfaceVisibility("hidden"), ...]}>hidden</div>
	</div>
</div>
```

### Building a flip card

Hide the back face of both sides of a card and turn the card around on hover. Hover the card:

```tsx
<div mix={[perspective(800)]}>
	<div
		mix={[
			zstack(),
			transformStyle(),
			transition("transform", { duration: 600 }),
			when(":hover > &", rotateY(180)),
		]}
	>
		<div mix={[backfaceVisibility(), ...]}>Front</div>
		<div mix={[backfaceVisibility(), rotateY(180), ...]}>Back</div>
	</div>
</div>
```

## Applying on a state

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

```ts
u.hover(u.backfaceVisibility())
```

## Responsive design

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

```ts
u.at("md", u.backfaceVisibility())
```

## Signature

```ts
u.backfaceVisibility(value?: BackfaceVisibilityValue)
```