A local demo page. The chart is drawn as a plain SVG <path>, exactly the way
Highcharts, D3 and the rest do it. The data is invented to exercise the physics:
two cliffs of different depth, a stepped climb and a spike.
Three series, %
Series C (flat)Series BSeries A
Ride
Your own track
Numbers in any separators: one series of values, or one x, y pair per line.
Decimals take a dot. Or load a track saved in the extension with E.