My video Target Tint was taking a beating over on 101questions with well over 50% skips. But the overall concept seemed solid to me. What happens when you apply multiple layers of tint? My guess is that people watched that video and figured the answer was a matter of simple division when, in fact, tint is more complicated and more interesting than that. If you wear two sunglasses with 50% tint each, for instance, are you then blind? So I reshot it and the result is now humming along at 90% perplexity as of this writing. Raise your hand if you dig the revise-and-resubmit cycle of teaching.
Here's the task page.