Enter three numbers in the format "a,b,c" in the textfield and press enter to see the topograph for ax2 + bxy + cy2. The button "Input/Output" can be used to switch between the vectors and values of the topograph. You can also drag one edge to another to shift the topograph. This is a bit unnatural, but if you view it in vector mode, it's easy to see how the shifts are working. While dragging, the areas in pink are where you can let go to move the topograph.