void HandleMove ( Vector2 _screenPos ) {
iTween.Stop (this.moveAnalog.gameObject,"move");
Vector2 delta = _screenPos - this.moveZone.center;
this.moveDir = delta.normalized;
float len = delta.magnitude;
Vector2 final_pos = this.moveZone.center + this.moveDir * Mathf.Min( len, this.moveLimitation );
Vector3 worldpos = this.hudCamera.ScreenToWorldPoint( new Vector3( final_pos.x, final_pos.y, 1 ) );
this.moveAnalog.position = new Vector3( worldpos.x, worldpos.y, this.moveAnalog.position.z );
}