The Khan Academy has just got rid of its popular streak metric. I woke up this morning in a somewhat ratty frame of mind and decided to soothe the savage breast by doing a few exercises on KA (which for a while now has had a feature that suggested exercises to review) - and discovered, with shock and dismay, that KA had completely changed the UI. It is much more sensible in one respect - the user is prodded into working through a group of exercises on a single subject, rather than reviewing the mixed bag of exercises hauled up by the algorithm. Unfortunately all this solid good sense is coupled with a new progress display consisting of stacks of leaves, which replaces the former streak bar (and the most recent streak bar was already a step in the wrong direction, replacing the ur-streak bar which told you how long a streak you had racked up).
Now honestly. If they were going to lavish this kind of ingenuity on the site, why not give us exercises on Laplace transforms? Or, to be slightly less esoteric, why not have a bank of exercises on integration? At present the site simply reinforces the bad mindset of the sort of person who does not use calculus on a daily basis - that is, the attitude that differentiation is the easy one and integration is to be approached with extreme caution, not to say trepidation. (There are currently NO exercises in integration.)
A while back I read a piece by a British mathematician who commented that the sense for how best to tackle integration came with maturity - one developed one's intuition by doing a wide variety of problems over the years. I was unfortunately introduced to integration at Smith, at a time when I was profoundly depressed, so I did not then lay down the foundation for this particular sort of mathematical maturity - but the comment filled me with hope. I felt that if I did problems on a daily basis intuition would come. And if such problems were readily available online, with instant feedback, I would probably be doing them on a daily basis. Paltry it may be, but it would be good for me to rack up a streak of a thousand or so. Well, it is salutary, no doubt, to be made to confront one's sloth: I expect there is a software package with a perfectly serviceable question bank, and sloth has led me down the path of least resistance.