public class ControlCamera : MonoBehaviour
{

private Vector2?[] oldTouchPositions = {
    null,
    null
};

private Vector2 oldTouchVector;

private float oldTouchDistance;

private Vector3 bottomLeft;
private Vector3 topRight;

private float cameraMaxY;
private float cameraMinY;
private float cameraMaxX;
private float cameraMinX;

public float maxZoom;
public float minZoom;

private void Start()
{
    //  Set max camera bounds
    topRight = GetComponent<Camera>().ScreenToWorldPoint(new Vector3(GetComponent<Camera>().pixelWidth, GetComponent<Camera>().pixelHeight, -transform.position.z));
    bottomLeft = GetComponent<Camera>().ScreenToWorldPoint(new Vector3(0, 0, -transform.position.z));
    cameraMaxX = topRight.x;
    cameraMaxY = topRight.y;
    cameraMinX = bottomLeft.x;
    cameraMinY = bottomLeft.y;
}

private void Update()
{
    //  No touches
    if (Input.touchCount == 0)
    {
        oldTouchPositions[0] = null;
        oldTouchPositions[1] = null;
    }
    //  1 Touch
    else if (Input.touchCount == 1)
    {
        if (oldTouchPositions[0] == null || oldTouchPositions[1] != null)
        {
            oldTouchPositions[0] = Input.GetTouch(0).position;
            oldTouchPositions[1] = null;
        }
        else
        {
            Vector2 newTouchPosition = Input.GetTouch(0).position;

            transform.position += transform.TransformDirection((Vector3)((oldTouchPositions[0] - newTouchPosition) * GetComponent<Camera>().orthographicSize / GetComponent<Camera>().pixelHeight * 2f));

            oldTouchPositions[0] = newTouchPosition;
        }
        //  2 touches or more
    } else {

        if (oldTouchPositions[1] == null)
        {
            oldTouchPositions[0] = Input.GetTouch(0).position;
            oldTouchPositions[1] = Input.GetTouch(1).position;
            oldTouchVector = (Vector2)(oldTouchPositions[0] - oldTouchPositions[1]);
            oldTouchDistance = oldTouchVector.magnitude;

        } else {

            Vector2 screen = new Vector2(GetComponent<Camera>().pixelWidth, GetComponent<Camera>().pixelHeight);

            Vector2[] newTouchPositions = {
                Input.GetTouch(0).position,
                Input.GetTouch(1).position
            };
            Vector2 newTouchVector = newTouchPositions[0] - newTouchPositions[1];
            float newTouchDistance = newTouchVector.magnitude;

            transform.position += transform.TransformDirection((Vector3)((oldTouchPositions[0] + oldTouchPositions[1] - screen) * GetComponent<Camera>().orthographicSize / screen.y));
            GetComponent<Camera>().orthographicSize *= oldTouchDistance / newTouchDistance;
            transform.position -= transform.TransformDirection((newTouchPositions[0] + newTouchPositions[1] - screen) * GetComponent<Camera>().orthographicSize / screen.y);

            oldTouchPositions[0] = newTouchPositions[0];
            oldTouchPositions[1] = newTouchPositions[1];
            oldTouchVector = newTouchVector;
            oldTouchDistance = newTouchDistance;

            // --------------------------------------------------------------->>

            //  Control Zoom In
            if (GetComponent<Camera>().orthographicSize > minZoom)
            {
                //
            }

            //  Control Zoom Out
            if (GetComponent<Camera>().orthographicSize < maxZoom)
            {
                //
            }

            // --------------------------------------------------------------->>
        }
    }

    //  Check if camera is out-of-bounds, if so, move back in-bounds
    topRight = GetComponent<Camera>().ScreenToWorldPoint(new Vector3(GetComponent<Camera>().pixelWidth, GetComponent<Camera>().pixelHeight, -transform.position.z));
    bottomLeft = GetComponent<Camera>().ScreenToWorldPoint(new Vector3(0, 0, -transform.position.z));

    if (topRight.x > cameraMaxX)
    {
        transform.position = new Vector3(transform.position.x - (topRight.x - cameraMaxX), transform.position.y, transform.position.z);
    }

    if (topRight.y > cameraMaxY)
    {
        transform.position = new Vector3(transform.position.x, transform.position.y - (topRight.y - cameraMaxY), transform.position.z);
    }

    if (bottomLeft.x < cameraMinX)
    {
        transform.position = new Vector3(transform.position.x + (cameraMinX - bottomLeft.x), transform.position.y, transform.position.z);
    }

    if (bottomLeft.y < cameraMinY)
    {
        transform.position = new Vector3(transform.position.x, transform.position.y + (cameraMinY - bottomLeft.y), transform.position.z);
    }
  }
}