Time for action – let's do some drawing!

Time to implement the drawing inside LineContainer.cpp. You will notice that this class already has most of its methods implemented, so you can save a little typing. I'll go over what these methods represent once we add the game's main update method. But basically LineContainer will be used to display the lines the player draws on screen to manipulate _rocket sprite, as well as display an energy bar that acts as a sort of timer in our game:

1. What we need to change here is the update method. So this is what you need to type inside that method:

   _energy -= dt * _energyDecrement;
   if (_energy < 0) _energy = 0;
   clear();
   
   switch (_lineType) {
     case LINE_NONE:
      break;
     case LINE_TEMP:
      drawLine(_tip, _pivot, Color4F(1.0, 1.0, 1.0, 1.0));
      drawDot(_pivot, 5, Color4F(Color3B::WHITE));
      break;
               
     case LINE_DASHED:
      drawDot(_pivot, 5, Color4F(Color3B::WHITE));
      int segments = _lineLength / (_dash + _dashSpace);
      float t = 0.0f;
     ...