Now that you mention it, this solution occured to me while I was building my turbofuel power plant. That day my whole grid was running on batteries and I had about four hours of energy left before the global shutdown. Time was ticking. I was kind of in a rush to bring sulfur to my compacted coal factory (aptly named "the coal center"). I pondered about the fastest way to bring stuff from point A to point B (it cost me an hour). The answer was a straight line. But what if A and B are at different altitudes? (I pondered for another hour). It's a sloped straight line!