I went completely overboard on this assignment. What was at first lots of fun to hack together was, in the end, a real chore to tidy up. Some parts are still a bit dirty. I have left all my comments and debug statements in due to lack of time (use Java Console to see debug statements). I have used a special comment (usually) when a comment is a note to me to do something. This special comment is '//!'.

Additional features as per assignment specification:
 

Provide visual feedback ("rubber banding").	Yes
Pick a colour for the next line.	Yes
Allow to selectively delete previously draw lines.	No. Only the last drawn object can be deleted using undo. This is however unlimited.

Other features:

• Selectable background colours
• Parameterised applet
• Also runs as an application
• Use of popup menus
• Double buffering (possibly should be called "triple buffering"). See Approach.
• Unlimited undo (which ended up being trivial). However, this only deletes the last inserted object. That is, it doesn't work for undoing a background colour change.

• Put in pre and post conditions. However, this wasn't in the assignment spec. I wrote a heap of code (created the first weekend after assignment release) before I find out that we had to do this. Please be forgiving.
• I wanted to use javadoc comments but I ran out of time.
• Just do one of the additional features. Sorry, I just got carried away.