Click the green flag to generate a random list of 8 numbers and watch it be sorted by the quicksort algorithm. The blue boxes represent the two numbers being compared at a given time, and the numbers on the bottom row represent the range of the list being sorted at any given time. The red lines represent where the list is subdivided.
Due to the limitations of Scratch and the fact that I didn't want to spend a long time refining all the details, the algorithm is not perfectly efficient (though from my testing it does look like it is correct, I haven't run into any test cases where it doesn't sort properly yet). If you want a detailed explanation of quicksort, check out https://en.wikipedia.org/wiki/Quicksort, and feel free to ask me any questions if you want to know more.