private void UpdateSelection()
{
    if (!Camera.main) return;

    RaycastHit hit;
    float raycastDistance = 25.0f;
    if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit, raycastDistance, LayerMask.GetMask("ChessPlane")))
    {
        selectionX = (int)hit.point.x;
        selectionY = (int)hit.point.z;
    }
    else
    {
        selectionX = -1;
        selectionY = -1;
    }
}