I used this activity on the first day of class in MTH 255H (multivariable calculus). It provided a nice introduction to representations of functions of several variables, even though I only had 10–15 minutes. I provided large whiteboards, but the students didn't really use them. The next class, I did a very quick (5 minute) wrapup covering the first few questions only. Despite the rush, I felt the activity helped set the tone for the course.