As the game is currently written, it is not always clear what type of shape the player is working with. To make the application easier to use, add a status bar control and use it to display a string identifying the currently selected shape.
The Graphics class allows you to create numerous other shapes besides rectangles, ellipses, and lines. Enhance the VC++ Doodle game to support other shapes, such as a pie, arc, and polygon. You can get information on the arguments that need to be supplied to create each of the shapes using Visual C++'s Help system.
The Visual C++ Pen and Brush classes provide access to dozens of predefined colors. Expand the VC++ Doodle game's list of supported colors to give the player additional choices.
Use the MessageBox::Show method to require the player to confirm his desire to clear the drawing area before allowing the btnClear_Click event function to execute.
Make the VC++ Doodle game a little more exciting by adding some sound effects. For example, consider playing the C:\Windows\Media\Tada.wav file when the application loads. Also, find a different sound to play when the player switches colors and when the player clicks on the button that clears the drawing surface.