You each got three scores: quiz---comments on existing code---explanation of pulsing circle.  Each ranged from 0 to 5.  If you did the extra credit there was a fourth score.

Most people did well on the quiz -- with a couple of minor mistakes. 

Most people who made comments did well.

Many of you thought through what was happening with the turtles going in circles. You all explained that that increasing or decreasing the speed made the turtles follow circles with different centers. But no one explained why the original circle seemed to grow and shrink. The answer is that even at different speeds and circling different centers the turtles were all always at the same distance from the original center! That's the case because they all deviated from the original circle in the same way.

Only one person had the courage to do the extra credit. Congratulations!