Danmaku_no_Kyojin.Collisions.CollisionConvexPolygon.Intersects C# (CSharp) Method

        private bool Intersects(CollisionCircle circle)
        {
            float radiusSquared = circle.Radius * circle.Radius;
            var vertex = GetWorldPosition(Vertices[Vertices.Count - 1]);
            var circleCenter = circle.GetCenter();
            float nearestDistance = float.MaxValue;
            bool nearestIsInside = false;
            int nearestVertex = -1;
            bool lastIsInside = false;

            for (int i = 0; i < Vertices.Count; i++)
            {
                var nextVertex = GetWorldPosition(Vertices[i]);
                var axis = circleCenter - vertex;
                float distance = axis.LengthSquared() - radiusSquared;

                if (distance <= 0)
                    return true;

                bool isInside = false;
                var edge = nextVertex - vertex;
                float edgeLengthSquared = edge.LengthSquared();

                if (!edgeLengthSquared.Equals(0))
                {
                    float dot = Vector2.Dot(edge, axis);

                    if (dot >= 0 && dot <= edgeLengthSquared)
                    {
                        var projection = vertex + (dot / edgeLengthSquared) * edge;

                        axis = projection - circleCenter;

                        if (axis.LengthSquared() <= radiusSquared)
                            return true;

                        if (edge.X > 0)
                        {
                            if (axis.Y > 0)
                                return false;
                        }
                        else if (edge.X < 0)
                        {
                            if (axis.Y < 0)
                                return false;
                        }
                        else if (edge.Y > 0)
                        {
                            if (axis.X < 0)
                                return false;
                        }
                        else
                        {
                            if (axis.X > 0)
                                return false;
                        }

                        isInside = true;
                    }
                }

                if (distance < nearestDistance)
                {
                    nearestDistance = distance;
                    nearestIsInside = isInside || lastIsInside;
                    nearestVertex = i;
                }

                vertex = nextVertex;
                lastIsInside = isInside;
            }

            if (nearestVertex == 0)
                return nearestIsInside || lastIsInside;

            return nearestIsInside;
        }

 private bool Intersects(CollisionConvexPolygon element)
 {
     return(element.Intersects(this));
 }