Thanks to @jk_herbert, @mrhodotnet, @MrPicc112, @mrautomatic and @mathhombre for the suggestions on Twitter.
Updated version addresses the following:
- Writing equation given slope and y-intercept places less cognitive demand on a student than writing the equation based on the graph. Levels 3 and 4 have been switched.
- Points and answers can't be changed after answer has been submitted.
- A running total has been added so student and teacher can view overall performance.
- Correct answer shown once answer is submitted giving immediate feedback to students on all levels.
There were also a couple of suggestions that were already embedded in the applet. There is a "reset" and "go to next level" button that can be accessed in the object properties. Double clicking on the applet should open it in a separate window which will allow you to save as well as make any changes you'd like.