Dear Khan Academy:

Much gratitude to you. I had never been able to grasp differential calculus until I found your site. Later you filled in the Calculus courses more, and, for the first time, I started to get the rudiments of integral calculus. Even so, I have months to go before I finish off those videos and questions.

Looking to the future, at this rate, perhaps a year from now, I'd like to try the multivariable calculus course, but I notice that most of the later modules in that course have no practice questions. Is there a plan to add the regular "mission" work and interactive questioning and "masters challenges" to that course to?

Thanks again for doing the impossible. (I failed Algebra 1 in 7th grade, so this is all far beyond what I ever thought possible given my learning blockages regarding math.)

Calculus Orphan.