This chart uses the showArea option to draw line, dots but also an area shape. Use the low option to specify a fixed lower bound that will make the area expand. You can also use the areaBase property to specify a data value that will be used to determine the area shape base position (this is 0 by default).
By naming your series using the series object notation with a name property, you can enable the individual configuration of series specific settings.
showArea and even the smoothing function can be overridden per series! And guess what? You can even override those series settings in the responsive configuration! Check the example code for more details.