ScrollingShooter.GameObjectManager.UpdateAxisLists C# (CSharp) Method

        private void UpdateAxisLists()
        {
            HashSet<CollisionPair> overlaps = new HashSet<CollisionPair>();
            int i, j;

            // Sort the vertical axis
            for (i = 1; i < verticalAxis.Count; i++)
            {
                Bound bound = verticalAxis[i];
                j = i - 1;

                // if our bound needs to be moved left... lower in the list
                while ((j >= 0) && verticalAxis[j].CompareTo(bound) > 0)
                {
                    // What are we passing, and what are we passing it with?
                    if (verticalAxis[j].Type == BoundType.Min && bound.Type == BoundType.Max)
                    {
                        // when a Max bound passes a min, we remove it from
                        // the collision set
                        collisions.Remove(new CollisionPair(verticalAxis[j].Box.GameObjectID, bound.Box.GameObjectID));
                        verticalOverlaps.Remove(new CollisionPair(verticalAxis[j].Box.GameObjectID, bound.Box.GameObjectID));
                    }
                    else if (verticalAxis[j].Type == BoundType.Max && bound.Type == BoundType.Min)
                    {
                        // when a Min bound passes a Max, we add it to the
                        // potential collision set
                        verticalOverlaps.Add(new CollisionPair(verticalAxis[j].Box.GameObjectID, bound.Box.GameObjectID));
                    }

                    // Shift the elment at j up the list by one index
                    verticalAxis[j + 1] = verticalAxis[j];
                    j--;
                }
                verticalAxis[j + 1] = bound;
            }

            // Check the potential overlaps for intersection
            foreach (CollisionPair pair in verticalOverlaps)
            {
                GameObject A = GetObject(pair.A);
                GameObject B = GetObject(pair.B);
                if (A.Bounds.Intersects(B.Bounds))
                {
                    collisions.Add(pair);
                }
            }
        }