In Class

Create a simple paint program.
The program should draw whenever the user presses the left mouse button, or moves the mouse while holding the button.
It should be able to draw in multiple colors - when the user hits 'r', set the current color to red; 'g' sets the color to green; 'b' sets the color to blue (as an example).

This is just a quick-and-dirty program. One thing that will make it simpler is to not use double-buffering.
Make sure not to clear the window every time something new is drawn.

Other optional features:

• Change the brush size using the arrow keys
• Provide different brush shapes, selected by other keys
• Erase instead of draw, when the control key is held down
• Save the drawing to a file before exiting