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Box-Circle Collision Detection

Collision with a circle may be one of the simpler ones. Because its projection is the same in all directions (it's simply the circle's radius), we can just do the following:

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private function refresh():void {     //prepare the vectors     var v:Vector2d;     var current_box_corner:Point;     var center_box:Point = box1.getDot(0);           var max:Number = Number.NEGATIVE_INFINITY;     var box2circle:Vector2d = new Vector2d(c.x - center_box.x, c.y - center_box.y)     var box2circle_normalised:Vector2d = box2circle.unitVector           //get the maximum     for (var i:int = 1; i < 5; i++)     {         current_box_corner = box1.getDot(i)         v = new Vector2d(             current_box_corner.x - center_box.x ,             current_box_corner.y - center_box.y);         var current_proj:Number = v.dotProduct(box2circle_normalised)                   if (max < current_proj) max = current_proj;     }     if (box2circle.magnitude - max - c.radius > 0 && box2circle.magnitude > 0) t.text = "No Collision"     else t.text = "Collision" }