Shiverz

1. Cộng đồng
2. Feature Requests and General Site Feedback
3. Suggestion

Also I know there is the argument that in real, official tests you can't restart. However I find Khan Academy's course challenges a place more to practice your skill sets rather than to actually do...

1. Cộng đồng
2. Technical Issues and Workarounds
3. Courses disappeared from dashboard

Same. For me it was my physics course. I dunno where it went, but when I went and looked, the whole course was removed and replaced with another course that I didn't have mastery on.