public void DrawCurtainGrid(Graphics graphics)
{
// draw the U grid lines
Pen lockBluePen = new Pen(System.Drawing.Color.Blue, m_lockedPenWidth);
Pen unlockBluePen = new Pen(System.Drawing.Color.Blue, m_unlockedPenWidth);
DrawULines(graphics, lockBluePen, unlockBluePen);
// draw the V grid lines
Pen lockbrownPen = new Pen(System.Drawing.Color.Brown, m_lockedPenWidth);
Pen unlockbrownPen = new Pen(System.Drawing.Color.Brown, m_unlockedPenWidth);
DrawVLines(graphics, lockbrownPen, unlockbrownPen);
// draw the boundary lines
Pen blackPen = new Pen(System.Drawing.Color.Black, m_boundaryPenWidth);
DrawBoundLines(graphics, blackPen);
// draw all the assistant line & display the hints
DrawAssistLine(graphics);
}