Guess sizes with a reference, then check the ratio
Anchor on the labelled reference. Estimate how many references fit along the measured dimension before moving the slider.
Keep units consistent
A 3 metre object beside a 1.5 metre reference is twice the reference. Comparing metres with centimetres without conversion creates an error of a hundred times.
Use ratios for feedback
Guessing twice the true value and half the true value are equally far away multiplicatively. Scale Sense scores both misses symmetrically.
Check what is measured
Height, length and area are different quantities. The launch questions label their dimension and cite a measurement source; the visual bar represents that dimension, not an unlabelled photographic perspective.