void BuildGround()
{
Obstacle o = groundPool.RequestFreeObstacle(ObstacleHeap);
if (o == null)
{
nextGroundLenght += 2f; return;
}
o.transform.position = new Vector3(nextGroundLenght, groundHeight + o._yHeightOffGround);
nextGroundLenght += o._width;
o.ActiveObstacle = true;
}
