---

        List<List<Vector2>> rows = BuildPositionRows(hexPositions, tolerance);

        for (int row = 0; row < rows.Count; row++)
        {
            List<Vector2> rowPositions = rows[row];
            rowPositions.Sort((left, right) => left.x.CompareTo(right.x));

            for (int i = 0; i < rowPositions.Count - 1; i++)
            {
                Vector2 left = rowPositions[i];
                Vector2 right = rowPositions[i + 1];
                if (Mathf.Abs((right.x - left.x) - xStep) > tolerance)
                {
                    continue;
                }

                Vector2 middle = (left + right) * 0.5f;
                TryAddPocket(pockets, hexPositions, new Vector2(middle.x, middle.y + rowStep), tolerance);
                TryAddPocket(pockets, hexPositions, new Vector2(middle.x, middle.y - rowStep), tolerance);
            }
        }

        return pockets;
    }

    private List<List<Vector2>> BuildPositionRows(List<Vector2> positions, float tolerance)
    {
        var rows = new List<List<Vector2>>();
        for (int i = 0; i < positions.Count; i++)
        {
            Vector2 position = positions[i];
            List<Vector2> row = FindPositionRow(rows, position.y, tolerance);
            if (row == null)
            {
                row = new List<Vector2>();
                rows.Add(row);
            }

            row.Add(position);
        }

        return rows;
    }

    private List<Vector2> FindPositionRow(List<List<Vector2>> rows, float z, float tolerance)
    {
        for (int i = 0; i < rows.Count; i++)
        {
            if (rows[i].Count > 0 && Mathf.Abs(rows[i][0].y - z) <= tolerance)
            {
                return rows[i];
            }
        }

        return null;
    }

    private void TryAddPocket(List<Vector2> pockets, List<Vector2> hexPositions, Vector2 candidate, float tolerance)
    {
        if (HasPosition(hexPositions, candidate, tolerance) || HasPosition(pockets, candidate, tolerance))
        {
            return;
        }

        pockets.Add(candidate);
    }

    private List<Vector2> ToCenteredPlanePositions(List<Vector2> positions, Vector2 center, float radius)
    {
        var centeredPositions = new List<Vector2>(positions.Count);
        for (int i = 0; i < positions.Count; i++)
        {
            centeredPositions.Add((positions[i] - center) * radius);
        }

        return centeredPositions;
    }