/**
* Calculates reduced radius of pie
*/
protected function Calc()
{
parent::Calc();
$this->explode_amount = min($this->radius_x - 10, $this->radius_y - 10, max(2, (int) $this->explode_amount));
$this->radius_y -= $this->explode_amount;
$this->radius_x -= $this->explode_amount;
}