There are many natural enhancements we could make to SketchPad . Here are a few of the simpler ones for you to try. Replace the four color checkboxes with a single Choice widget. Allow erasing, by including another color choice that will set the pen color to the color of the background. Change the program so that if the Shift key is held down when an arrow key is pressed, a line 10 pixels long will be drawn.
Most modern programs give the user the ability to undo the last operation.
Implement an Undo command, activated by a button you'll add to the applet. In the interests of not confusing you about events, we did everything we could in SodaPop to hide the event-handling. The result, unfortunately, was a program that was nowhere as clean as it could have been. Go back to SodaPop and make the event handling as tidy as possible. A real drawing program allows the user to draw more than just curves and lines.