i want to check if a 2d sprite is facing the camera or turned away from it.

this will let me swap the image when the sprite is at 90° (in any axis)from the camera giving me a two sided sprite.

here are some of the things i have tried:

```
void CheckFlip()
{
// this won't work because reading euler angles can give nonsense results
//if (Mathf.Abs(transform.rotation.eulerAngles.x) > 90f ||
// Mathf.Abs(transform.rotation.eulerAngles.y) > 90f)
//// this dosent work becauses it flips when the z axis is rotated
//if (Mathf.Abs(Quaternion.Angle(transform.rotation, Quaternion.identity)) > 90f)
//// this dosent work either becuase it still flips when the z axis is rotated
// if (Quaternion.Dot( transform.rotation, Quaternion.Euler(90,90,0)) <= 0||
// Quaternion.Dot(transform.rotation, Quaternion.Euler(-90, -90, 0)) <= 0)
// this dosent work either becuase it still flips when the z axis is rotated
if (Mathf.Abs(Quaternion.Angle(transform.rotation, Quaternion.identity)) > 90f)
{
spriteRenderer.sprite = backSprite;
}
else
{
spriteRenderer.sprite = faceSprite;
}
}
```