The Mysterious EV Range Gauge

For a short time I drove (if I remember correctly in the late 90's) an Opel (US people read GM, UK read Vauxhall) Astra with a particularly stupid boad computer that showed remaining range on a central amber colour display based directly on instant fuel consumption, seemingly there wasn't any kind of "buffer" (or whatever more modern cars have) to level down the peaks.

Driving that on a mixed plain/hill road resulted easily in having some 200 km differences in remaining range, when fuel was actually low it was entertaining, like going uphill with 15-20 km remaining (scary), and then, downhill, going back to 200-220 (pheew, ok), then 100-120 on the plain and then back to 15 at next hill, and so on.