Two real things, one tap. Pick the bigger one and the measurements settle it.
Bigger here means the longest single dimension of each thing. The pictures are not to scale until you choose.
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A bigger or smaller game only asks you to pick a direction: two real objects appear, you tap the one you think is larger, and the real measurements settle it. There is no slider, no number to type and nothing to remember.
Yes. Free in your browser, no account, no daily cap. One tap per round means you can get through dozens of rounds in a few minutes.
The longest single dimension — the body length of an animal, the height of a building, the span of a vehicle. Every number is either a measurement from a public source or a value this library states it uses, and both are listed on the object library page.
That is what it is built for. The whole game is one tap on the bigger half of the screen; nothing needs a keyboard, a slider or a steady thumb.
Because a gap you can already see is not a game. Most rounds are within a factor of two of each other, which is roughly the range where the human eye stops being reliable about scale.
A slider asks for a steady thumb, a large screen and a moment of precision. A tap asks for none of those. That is why the two-choice version is the one people actually finish on a commute: the input costs a fraction of a second, so the round can cost a fraction of a second, and a bad answer costs nothing but one more tap.
It also changes what you are testing. A slider measures how precisely you can reproduce a ratio. Two choices only measure which way you lean — and which way you lean, on pairs that are genuinely close, is the honest version of whether you have any feel for scale at all.
The first pair is a bald eagle’s wingspan, 2.04 m, beside an emperor penguin’s standing height, 1.2 m. Later pairs can include a value this library states it uses. The score is only which one is longer.
Every number is either a measurement from a public source or a value this library states it uses, and both are listed on the object library page. The figures are shown after each round.