Manipulate the sliders to change the slope of the line. You may do this by dragging the point on the slider to the left or right, or you may do this by selecting the slider and using your arrow keys.
As you change the slope, observe how the size of the residuals (represented as the length of the vertical line between the point and the line), the size of the corresponding squares, and the total area of the squares (enumerated as TotalSquareError) change as the slope changes.

What do you think the "line of best fit" might be for these points?