I know this is a copy of a post from 5 years ago, but there many people misunderstood the idea: I was considering a way of unlocking things (like backgrounds, accessories, etc...) when you reach a certain amount of energy points. For example, you could get a background when you reach 100,000 energy points. One key thing here is you can't buy energy points and you can only get them by completing lessons and exercises, and that when you unlock something, you don't lose energy points. I just reached 250,000 energy points, the final tier of profile pictures on Khan Academy, and now energy points are worthless. 

~ Thank you KA Team in advance. ~